OSHA Instruction CPL 2.106
February 9, 1996
Office of Health Compliance Assistance
SUBJECT: Enforcement Procedures and Scheduling for Occupational Exposure
to Tuberculosis
A. Purpose. This instruction provides uniform inspection procedures
and guidelines to be followed when conducting inspections and issuing
citations under Section 5(a)(1) of the OSH Act and pertinent standards
for employees who are occupationally exposed to tuberculosis.
B. Scope. This instruction applies OSHA-wide.
C. References.
1. OSHA Instruction CPL 2.103, September 26, 1994, Field Inspection
Reference Manual (FIRM).
2. OSHA Instruction CPL 2.45B, June 15, 1985, The Revised Field
Operations Manual (FOM).
3. American Public Health Association - 1990 or current edition,
Control of Communicable Diseases in Man.
4. OSHA Instruction CPL 2-2.20B, CH-3, August 22, 1994.
Occupational Safety and Health Administration Technical Manual
Chapter No. 7.
5. OSHA Instruction, ADM 1-31, the IMIS Enforcement Data Processing
Manual.
6. OSHA Instruction ADM 1-32, Enforcement User Skills Manual (for
those Area Offices still using the NCR system).
7. Centers for Disease Control and Prevention (CDC), Biosafety in
Microbiological and Biomedical Laboratories, 3rd Edition, or
current edition.
8. Department of Health and Human Services, Public Health Service,
42 CFR Part 84; Final Rule
9. Centers for Disease Control and Prevention (CDC); Guidelines for
Preventing the transmission of mycobacterium tuberculosis in
Health Care Facilities, 1994; MMWR October 26, 1994 Vol. 43,
No. RR-13.
D. Action. OSHA Regional Administrators and Area Directors shall use
this instruction to ensure uniformity when performing inspections for
occupational exposures to tuberculosis (TB). The Directorate of
Compliance Programs shall provide support as necessary to assist the
Regional Administrators and Area Directors in enforcing this directive.
Issuance of this directive cancels the Memorandum to Regional
Administers dated October 8, 1993, and entitled Enforcement Policy and
Procedures for Occupational Exposure to Tuberculosis.
E. Federal Program Change. This is a federal program change which
impacts state programs.
1. The Regional Administrator (RA) shall ensure that this change is
promptly forwarded to each state designee using a format
consistent with the Plan Change Two-way Memorandum in Appendix A,
State Plan Policies and Procedures Manual (SPM).
2. The RA shall explain the content of this change to the state
designee as required.
3. The state shall respond to this change within 70 days in
accordance with paragraph I.1.a.(2).(a). and (b)., Part I,
Chapter III of the SPM.
4. The state's acknowledgment shall include (a) the state's plan
to adopt and implement an identical change, (b) the state's plan
to develop an alternative, which is as effective, or the reasons
why no change is necessary to maintain a program which is as
effective. The state shall submit a plan supplement within six
months in accordance with I.1.a.(3).(c)., Part I, Chapter III of
the SPM.
5. The RA shall advise state designees of the following:
a. In order to ensure a sound and consistent national
enforcement and litigation strategy in relation to complex
issues addressed by this instruction, state implementation of
the procedures in this instruction, or comparable state
procedures, must be carefully coordinated with OSHA.
b. The state is also responsible for extending coverage under
its procedures for addressing occupational exposure to
tuberculosis to the public sector employees in workplaces
covered by this instruction.
c. The Directorate of Technical Support is available to assist
the states in locating expert witnesses (see paragraph M.,
expert witnesses). Also, the Directorate of Compliance
Programs will provide support to the states through the RA
to assist in the enforcement of this directive.
6. The RA shall review policies, instructions, and guidelines issued
by the state to determine that this change has been communicated
to state compliance personnel.
F. Definitions. For a complete list of definitions applicable to
tuberculosis please refer to the list of definitions in the 1994
CDC guidelines found in Appendix A beginning on page 113.
G. Background. Since 1985, the incidence of tuberculosis (TB) in the
general U.S. population has increased approximately 14 percent,
reversing a 30-year downward trend. In 1993, 25,313 new cases of TB
were reported in the United States. Increases in the incidence of TB
have been observed in some geographic areas; these increases are
related partially to the high risk for TB among immunosuppressed
persons, particularly those infected with human immunodeficiency virus
(HIV). Other factors (e.g., socioeconomic) have also contributed to
these increases. Outbreaks have occurred in hospitals, correctional
institutions, homeless shelters, nursing homes, and residential care
facilities for AIDS patients. During 1994 and 1995 there has been a
decrease in the number of TB cases in the United States that is likely
been due to increased awareness and efforts in the prevention and
control of TB, including the implementation of TB control measures
recommended by the CDC and required by OSHA.
Recently, drug resistant strains of M. tuberculosis have become a
serious concern and cases of multi-drug-resistant (MDR) TB have
occurred in forty states. In a recent New York City study, 33% of
cases had organisms resistant to the two most effective drugs
available for treating the disease.
When organisms are resistant to both drugs, the course of the treatment
increases from six months to 18-24 months, and the cure rate decreases
from 100% to 60% or less.
In a 1992 American Hospital Association survey/CDC survey, 90 of 729
(13%) respondents reported nosocomial TB transmission to health care
workers. More than 80% of those facilities experienced TB skin test
conversions among workers. More than 100 cases of active TB disease
in health care workers were known to CDC and reported to Congress by
Dr. William Roper in the Spring of 1993. Twelve (12) health care
workers have died. Nationwide, at least several hundred employees have
become infected and required medical treatment after workplace exposure
to TB. In general, persons who become infected with TB have
approximately a 10% risk for developing active TB in their lifetimes.
M. tuberculosis is carried through the air in tiny infectious droplet
nuclei of 1 to 5 microns in diameter. These droplets may be generated
when a person with pulmonary and laryngeal TB disease coughs, speaks,
sings, sneezes, or spits. When inhaled by susceptible persons, the
mycobacteria in these droplets may become established in the lungs and,
in some cases, spread throughout the body. After an interval of
months, years, or even decades, the initial infection may then
progress to clinical illness (i.e., tuberculosis disease). Transmission
of TB is most likely to occur from persons with pulmonary or laryngeal
TB that are not on effective anti-TB therapy and who have not been
placed in respiratory isolation.
In occupational healthcare settings, where patients with TB are seen,
workers exposed to tuberculosis droplet nuclei are at increased risk
of infection with exposure to TB. Certain high-risk medical procedures
that are cough-inducing or aerosol generating can further increase the
risk of infection in health-care workers.
The employer's obligations are those set forth in the Occupational
Safety and Health Act (OSH Act) of 1970. Recommendations for
preventing the transmission of TB for health care settings were
originally established with the 1990 CDC Guidelines. In October, of
1994, those guidelines were revised and published (Appendix A). The
new guidelines emphasize the control of TB through an effective TB
infection control program. Under these guidelines the control of TB
is to be accomplished through the early identification, isolation, and
treatment of persons with TB, use of engineering and administrative
procedures to reduce the risk of exposure, and through the use of
respiratory protection. OSHA believes these guidelines reflect an
industry recognition of the hazard as well as appropriate, widely
recognized, and accepted standards of practice to be followed by
employers in carrying out their responsibilities under the OSH Act.
H. Inspection Scheduling and Scope
1. The evaluation of occupational exposure to TB shall be conducted
in response to employee complaints, related fatality/catastrophes,
or as part of all industrial hygiene inspections conducted in
workplaces where the CDC has identified workers as having a greater
incidence of TB infection than in the general population. The
degree of risk of occupational exposure of a worker to TB will
vary based on a number of factors discussed in detail by the CDC
(Appendix A, pg. 4-5). These workplaces have been the subject of
reports issued by the CDC which provide recommendations for the
control of tuberculosis. Specifically, these workplaces are as
follows:
a. health care facilities
b. correctional institutions
c. long-term care facilities for the elderly
d. homeless shelters
e. drug treatment centers
Note: Health-care facilities include hospitals where
patients with confirmed or suspect TB are treated or to which
they are transported. Coverage of non-hospital health care
settings (i.e., doctors' offices, clinics, etc.) includes only
personnel present during the performance of high hazard
procedures on suspect or active TB patients. Dental health care
personnel are covered by the directive only if they treat suspect
or active patients in a hospital or correctional facility.
Homeless shelters - due to a variety of circumstances, the control
of TB in homeless shelters presents unique problems for the
protection of workers. Shelters must establish protocols that
provide for rapid early identification followed by immediate
transfer of suspect cases if the shelters have elected not to
treat these patients.
2. All inspections in these workplaces shall include a review of the
employer's plans for employee TB protection, if any. Such plans
may include the infection control program, respiratory protection
and skin testing. Employee interviews and site observations are
an integral part of the process evaluation.
3. Complaints received from state and local government employees who
are outside federal jurisdiction in federal enforcement states
shall be referred to the appropriate agency by the Area Office.
I. Inspection Procedures. The procedure given in the FIRM, Chapter
II, shall be followed except as modified in the following sections:
1. Health care facilities generally have internal infection control
and employee health programs. This function may be performed by
a team or individual. Upon entry, the CSHO shall request the
presence of the infection control director and employee
occupational health professional responsible for occupational
health hazard control. Other individuals who will be responsible
for providing records pertinent to the inspection may include:
training director, facilities engineer, director of nursing, etc.
2. The CSHO shall establish whether or not the facility has had a
suspect or confirmed TB case within the previous six (6) months
from the opening conference to determine coverage under the OSH
Act. This determination may be based upon interviews and, in a
hospital, a review of the infection control data.
3. If the facility has had a suspect or confirmed TB case within the
previous six months, the CSHO shall proceed with the TB portion
of the inspection. The CSHO shall verify implementation of the
employer's plans for TB protection through employee interviews and
direct observation where feasible. Professional judgment shall be
used to identify which areas of a facility must be inspected
during the walkthrough (e.g., emergency rooms, respiratory
therapy areas, bronchoscopy suites, and morgue). After review of
the facility plans for worker TB protection, employee interviews
combined with an inspection of appropriate areas of the facility,
shall be used to determine compliance.
4. CSHOs who perform smoke-trail visualization tests should review
the protocol in Appendix B of this directive.
5. CSHOs should be prepared to present to the employer the material
safety data sheet (MSDS) for the smoke that is released on a
smoke-trail visualization.
J. Compliance Officer Protection
1. Area Directors or Assistant Area Directors shall ensure that
CSHOs performing TB related inspections are familiar with the CDC
Guidelines, terminology, and are adequately trained through
either course work or field/work experience in health care
settings. Consultation with the regional TB coordinators is
encouraged prior to beginning such inspections.
2. CSHOs shall not enter occupied respiratory isolation [AFB (acid
fast bacilli)] rooms to evaluate compliance unless, in their
determination entry is required to document a violation. Prior to
entry CSHOs will discuss the need for entry with the Area Director.
Photographs or video taping where practical shall be used for case
documentation. Under no circumstances shall photographing or
videotaping of patients be done. CSHO's must take all necessary
precautions to assure and protect patient confidentiality.
3. CSHOs shall exercise professional judgement and extreme caution
when engaging in activities that may involve potential exposure to
TB. CSHOs normally shall establish the existence of hazards and
adequacy of work practices through employee interviews and shall
observe them in a manner which prevents exposure (e.g., through
an observation window where available).
4. On rare occasions when entry into potentially hazardous areas is
judged necessary (e.g., where the CSHO determines that direct
observation of a high hazard procedure is necessary), the CSHO
shall be properly equipped as required by the facility, this
directive, and following consultation with the CSHO's supervisor.
Since CSHOs' respiratory protection is used in more than one type
of industry they shall use their negative pressure elastomeric
face piece respirators equipped with HEPA filters as the minimum
level of respiratory protection.
5. CSHOs who conduct TB inspections shall have been offered the TB
skin tests. CSHOs exposed to an individual(s) with active
infectious TB shall receive a follow-up examination and follow
Sections J. and K. of Appendix A beginning on page 37.
Note: A "TB Skin Test" means the intradermal injection (Mantoux
Method) of tuberculin antigen (usually PPD) with subsequent
measurement of the induration by designated, trained personnel.
6. If an isolation room is occupied by a patient with confirmed or
suspect TB or has not been adequately purged when a smoke-trail
test is performed, then the CSHO should assume that the
isolation room is not under negative pressure. Under such
circumstances CSHOs shall wear a negative pressure HEPA respirator
when performing air tests as described in Appendix B or if entry
into the room is determined to be necessary.
K. Citation Policy. Relevant chapters of the FIRM shall be followed
when preparing and issuing citations for hazards related to TB.
1. The following requirements apply when citing hazards found in
target workplaces. Employers must comply with the provisions of
these requirements whenever an employee may be occupationally
exposed to TB:
Section 5(a)(1) -- General Duty Clause and Executive Order
12196, Section 1-201(a) for Federal facilities.
29 CFR 1910.134 -- Respiratory Protection
29 CFR 1910.145 -- Accident Prevention Signs and Tags
29 CFR 1910.20 -- Access to Employee Exposure and Medical Records
29 CFR 1904 -- Recording and Reporting Occupational Injuries
& Illness
L. Violations. All elements in this section must be addressed to
ensure adequate protection of employees from TB hazards. Violations of
these OSHA requirements will normally be classified as serious.
1. General Duty Clause - Section 5(a)(1). Section 5(a)(1)
provides: "Each employer shall furnish to each of his employees
employment and a place of employment which are free from
recognized hazards that are causing or are likely to cause death
or serious physical harm to his employees."
a. Section 5(a)(1) citations must meet the requirements outlined
in the FIRM, and shall be issued only when there is no
standard that applies to the particular hazard. The hazard,
not the absence of a particular means of abatement, is the
basis for a general duty clause citation. All applicable
abatement methods identified as correcting the same hazard
shall be issued under a single 5(a)(1) citation.
b. Recognition, for purposes of citing section 5(a)(1), is shown
by the CDC Guidelines for the types of exposures detailed
below because the CDC is an acknowledged body of experts
familiar with the hazard.
c. Citations shall be issued to employers with employees working
in one of the workplaces where the CDC has identified workers
as having a higher incidence of TB infection than the general
population, when the employees are not provided appropriate
protection and who have exposure as defined below:
1. Exposure to the exhaled air of an individual with
suspected or confirmed pulmonary TB disease, or
Note: A suspected case is one in which the facility
has identified an individual as having symptoms
consistent with TB. The CDC has identified the
symptoms to be: productive cough, coughing up blood,
weight loss, loss of appetite, lethargy/weakness,
night sweats, or fever.
2. Employee exposure without appropriate protection to a
high hazard procedure performed on an individual with
suspected or confirmed infectious TB disease and which
has the potential to generate infectious airborne
droplet nuclei. Examples of high hazard procedures
include aerosolized medication treatment, bronchoscopy,
sputum induction, endotracheal intubation and suctioning
procedures, emergency dental, endoscopic procedures, and
autopsies conducted in hospitals.
d. If a citation under 5(a)(1) is justified, the citation,
after setting forth the SAVE for section 5(a)(1), shall
state:
Section 5(a)(1) of the Occupational Safety and Health Act
of 1970: The employer did not furnish employment and a
place of employment which were free from recognized hazards
that were causing or likely to cause death or serious
physical harm to employees exposed to the hazard of being
infected with Mycobacterium tuberculosis through
unprotected contact with [specify group such as
patients, inmates, clients, etc.] who was/were infectious
or suspected to be infectious with tuberculosis in that:
[list deficiencies]
Feasible and useful abatement methods for reducing this
hazard, as recommended by the CDC, include, but are not
limited to: [list abatement methods].
e. The following are examples of feasible and useful abatement
methods, which must be implemented to abate the hazard.
Deficiencies found in any category can result in the
continued existence of a serious hazard and may, therefore,
allow citation under 5(a)(1).
1. Early Identification of Patient/Client. The employer
shall implement a protocol for the early identification
of individuals with active TB. See Appendix A pages
19-30.
2. Medical Surveillance:
a. Initial Exams. The employer, in covered workplaces,
shall offer TB skin tests (at no cost to the
employees) to all current potentially exposed
employees and to all new employees prior to
exposure. A two-step baseline shall be used for
new employees who have an initially negative PPD
test result and who have not had a documented
negative TB skin test result during the preceding
12 months (See Appendix A, pg. 63). TB skin tests
shall be offered at a time and location convenient
to workers. Follow-up and treatment evaluations
are also to be offered at no cost to the workers.
Note: The reading and interpretation of the
TB skin tests shall be performed by a qualified
individual as described in the CDC Guidelines.
b. Periodic Evaluations. TB skin testing shall be
conducted every three (3) months for workers in
high risk categories, every six (6) months for
workers in intermediate risk categories, and
annually for low risk personnel (The CDC has
defined the criteria for high, intermediate, and
low risk categories, see Appendix A, pg. 8-17).
Workers with a documented positive TB skin test
who have received treatment for disease or
preventive therapy for infection are exempt from
the TB skin test but must be informed periodically
about the symptoms of TB and the need for immediate
evaluation of any pulmonary symptoms suggestive of
TB by a physician or trained health care provider
to determine if symptoms of TB disease have
developed.
Note: If the facility has not completed a risk
assessment the CSHO shall review the TB related
records to establish required testing frequencies
for the facility and areas of the facility.
c. Reassessment following exposure or change in
health. Workers who experience exposure to an
individual with suspect or confirmed infectious TB
for whom infection control precautions have not
been taken shall be managed according to CDC
recommendations (Appendix A). An employee who
develops symptoms of TB disease shall be
immediately evaluated according to the CDC
Guidelines.
3. Case Management of Infected Employees shall include
the following:
a. Protocol for New Converters. Conversion to a
positive TB skin test shall be followed as soon as
possible, by appropriate physical, laboratory, and
radiographic evaluations to determine whether the
employee has infectious TB disease. (See Appendix
A, pg. 65).
b. Work Restrictions for Infectious Employees. See
Appendix A, page 41.
4. Worker Education and Training. Training and
information to ensure employee knowledge of such issues
as the mode of TB transmission, its signs and symptoms,
medical surveillance and therapy, and site specific
protocols including the purpose and proper use of
controls shall be provided to all current employees and
to new workers upon hiring. (See Appendix A, pgs. 36-37)
Training should be repeated as needed.
Workers shall be trained to recognize, and report to a
designated person, any patients or clients with
symptoms suggestive of infectious TB and instructed on
the post exposure protocols to be followed in the
event of an exposure incident. (See Appendix A, pg. 23)
5. Engineering Controls. The use of each control measure
must be based on its ability to abate the hazard.
a. Individuals with suspected or confirmed infectious
TB disease must be placed in a respiratory
acid-fast bacilli (AFB) isolation room. High hazard
procedures on individuals with suspected or
confirmed infectious TB disease must be performed
in AFB treatment rooms, AFB isolation rooms, booths,
and/or hoods. AFB isolation refers to a negative
pressure room or an area that exhausts room air
directly outside or through HEPA filters if
recirculation is unavoidable.
b. Isolation and treatment rooms in use by individuals
with suspected or confirmed infectious TB disease
shall be kept under negative pressure to induce
airflow into the room from all surrounding areas
(e.g., corridors, ceiling plenums, plumbing chases,
etc.). (See Appendix A, Supplement No. 3, page 76)
Note: The employer must assure that AFB
isolation rooms are maintained under negative
pressure. At a minimum, the employer must use
nonirritating smoke trails or some other indicator
to demonstrate that direction of airflow is from
the corridor into the isolation/treatment room with
the door closed. If an anteroom exists, direction
of airflow must be demonstrated at the inner door
between the isolation/treatment room and the
anteroom. (See Appendix B)
c. Air exhausted from AFB isolation or treatment
rooms must be safely exhausted directly outside and
not recirculated into the general ventilation
system. (See Appendix A, Supplement No. 3, page
87).
In circumstances where recirculation is unavoidable,
HEPA filters must be installed in the duct system
from the room to the general ventilation system.
(See Appendix A, Supplement No. 3, page 82). For
these HEPA filters, a regularly scheduled monitoring
program to demonstrate as-installed effectiveness
should include; 1) recognized field test method, 2)
acceptance criteria, and 3) testing frequencies
(see Appendix A, Supplement No. 3, page 85). The
air handling system should be appropriately marked
with a TB warning where maintenance personnel
would have access to the duct work, fans, or
filters for maintenance or repair activities.
d. In order to avoid leakage, all potentially
contaminated air which is ducted through the
facility must be kept under negative pressure until
it is discharged safely outside (i.e., away
from occupied areas and air intakes), or
e. The air from isolation and treatment rooms must be
decontaminated by a recognized process (e.g., HEPA
filter) before being recirculated back to the
isolation/treatment room. The use of UV radiation
as the sole means of decontamination shall not be
used. The CDC Guidelines allow the use of UV in
waiting rooms, emergency rooms, corridors, and the
like where patients with undiagnosed TB could
potentially contaminate the air. (See appendix A,
pg. 90)
Note: The opening and closing of doors in an
isolation or treatment room which is not equipped with
an anteroom compromises the ability to maintain negative
pressure in the room. For these rooms, the employer
should utilize a combination of controls and practices
to minimize spillage of contaminated air into the
corridor. Recognized controls and practices include,
but are not limited to: minimizing entry to the room;
adjusting the hydraulic closer to slow the door
movement and reduce displacement effects; adjusting
doors to swing into the room where fire codes permit;
avoiding placement of room exhaust intake near the
door; etc.
f. If high-hazard procedures are performed within
AFB isolation or treatment rooms without benefit
of source control ventilation or local exhaust
ventilation (e.g., hood, booth, tent, etc.), and
droplets are released into the environment (e.g.,
coughing), then a purge time interval must be
imposed during which personnel must use a
respirator when entering the room. (See Appendix
A, pg. 35 and Suppl. 3, Table S3-1)
g. Interim or supplemental ventilation units equipped
with HEPA filters as described in Appendix A pgs.
70-73 are acceptable.
2. Respiratory Protection - 29 CFR 1910.134(a)(2) and (b).
The standard provides in part:
"Respirators shall be provided by the employer when such
equipment is necessary to protect the health of the employee. The
employer shall provide the respirators which are applicable and
suitable for the purpose intended. The employer shall be
responsible for the establishment and maintenance of a respiratory
protective program which shall include the requirement outlined in
paragraph (b) of this section."
a. Requirements for a minimal acceptable program. The 1994
CDC Guidelines specify standard performance criteria for
respirators for exposure to TB. These criteria include (see
appendix A pg 97):
1. The ability to filter particles 1 um in size in the
unloaded state with a filter efficiency of greater than
or equal to 95% (i.e., filter leakage of less than or
equal to 5%), given flow rates of up to 50L per minute.
2. The ability to be qualitatively or quantitatively fit
tested in a reliable way to obtain a face-seal leakage
of less than or equal to 10%.
3. The ability to fit the different facial sizes and
characteristics of health care workers which can usually
be met by making the respirators available in at least
three sizes.
4. The ability to be checked for face piece fit, in
accordance with OSHA standards and good industrial
hygiene practice, by health care workers each time they
put on their respirator.
b. Under the new NIOSH criteria, filter materials would be
tested at a flow rate of 85 L/minute for penetration by
particles with a median aerodynamic diameter of 0.3 um and,
if certified would be placed in one of the following
categories: Type 100 (99.7% efficient), Type 99 (99%
efficient), and Type 95 (95% efficient). NIOSH has
determined that these categories of respirators are effective
against TB. Based upon these criteria, the minimally
acceptable level of respiratory protection for TB is the
Type 95 Respirator. The classes of these air-purifying,
particulate respirators to be certified are described under
42 CFR Part 84 Subpart K. See Volume 60 of the Federal
Register, page 30338 (June 8, 1995). Until these classes of
respirators are commercially available the minimal acceptable
respiratory protection meeting the criteria will remain the
HEPA respirator (see Appendix A, pg 98). The following
respiratory protection measures must be addressed:
1. Employees wear HEPA or respirators certified under 42
CFR Part 84 Subpart K in the following circumstances:
a. When workers enter rooms housing individuals with
suspected or confirmed infectious TB.
b. When workers are present during the performance of
high hazard procedures on individuals who have
suspected or confirmed infectious TB.
c. When emergency-medical-response personnel or others
transport, in a closed vehicle, an individual with
suspected or confirmed infectious TB.
Note: If a facility chooses to use disposable
respirators as part of their respiratory protection
program, their reuse by the same health care worker is
permitted as long as the respirator maintains its
structural and functional integrity and the filter
material is not physically damaged or soiled. The
facility must address the circumstances in which a
disposable respirator will be considered to be
contaminated and not available for reuse.
2. The following sample language is provided for citations
which are warranted under 1910.134(a)(2):
"The employer did not provide respirators which were
applicable and suitable for the purpose intended, nor
was a respiratory protection program established which
included the requirements outlined in 29 CFR 1910.134(b):
(a) Employees were given a [surgical mask or list
manufacturer/model number] respirator for protection
against airborne Mycobacterium tuberculosis when
entering isolation rooms or performing high hazard
procedures [including vehicular transporting if
applicable]. They shall use NIOSH approved respirators
(HEPA or those certified under 42 CFR Part 84 Subpart
K).
NIOSH approved respirators providing greater protection
would also be acceptable.
3. When respiratory protection (including disposable
respirators) is required, a complete respiratory
protection program must be in place in accordance with
29 CFR 1910.134(b).
3. Access to employee medical and exposure records: 29 CFR 1910.20.
a. A record concerning employee exposure to TB is an employee
exposure record within the meaning of 29 CFR 1910.20.
b. A record of TB skin test results and medical evaluations and
treatment are employee medical records within the meaning of
29 CFR 1910.20. Where known, the workers exposure record
should contain a notation of the type of TB, to which the
employee was exposed to (e.g., multidrug resistant TB).
c. These records shall be handled according to 29 CFR 1913.10 in
order for the CSHO to determine compliance with 29 CFR
1910.20.
4. Accident prevention signs and tags: 29 CFR 1910.145.
a. In accordance with 1910.145(f)(8), a warning shall be posted
outside the Respiratory isolation or treatment room.
1910.145(f)(4) requires that a signal word (i.e. "STOP",
"HALT", or "NO ADMITTANCE") or biological hazard symbol be
presented as well as a major message (e.g., "special
respiratory isolation", "Respiratory isolation", or AFB
isolation). A description of the necessary precautions,
e.g., respirators must be donned before entering.
Respiratory isolation rooms in an emergency department or
a message referring one to the nursing station for
instruction must also be posted.
b. The employer shall also use biological hazard tags on air
transport components (e.g., fans, ducts, filters) which
identify TB hazards to employees associated with working on
air systems that transport contaminated air (See Appendix A,
page 85).
c. The standard provides in part:
29 CFR 1910.145(e)(4): Biological hazard warning signs were
not used to signify the actual or potential presence of a
biohazard and to identify equipment, containers, rooms,
materials, experimental animals, or combinations thereof,
which contain, or are contaminated with viable hazardous
agents:
Sample violation language:
a. On or about [date], warning signs posted outside
respiratory (Respiratory) isolation or treatment rooms
did not state the entry requirement of wearing HEPA
filtered respirators.
Abatement Note: Warning signs must be posted on
respiratory isolation or treatment rooms stating "pulmonary
isolation", "respiratory isolation," or "AFB isolation."
The sign must state specifically the precautions required to
interact with those patients. Indicators on patient records
or tags on corpses, printed in language or symbols easily
recognized by employees are additional methods to achieve
this purpose.
5. OSHA 200 log - 29 CFR 1904:
a. For OSHA Form 200 record keeping purposes, both tuberculosis
infections (positive TB skin test) and tuberculosis disease
are recordable in the high risk setting referenced in
section H.1. A positive skin test for tuberculosis, even on
initial testing (except pre-assignment screening) is
recordable on the OSHA 200 log because there is a presumption
of work-relatedness in these settings unless there is clear
documentation that an outside exposure occurred.
Note: In this case preassignment means the same as pre
employment and initial testing is the same as baseline
testing.
b. If the employee's tuberculosis infection which was entered on
the OSHA 200 log progresses to tuberculosis disease during
the five-year maintenance period, the original entry for the
infection shall be updated to reflect the new information.
Because it is difficult to determine if tuberculosis disease
resulted from the source indicated by the skin test
conversion or from subsequent exposures, only one case
should be entered to avoid double counting.
c. A positive TB skin test provided within two weeks of
employment does not have to be recorded on the OSHA 200
forms. However, the initial test must be performed prior to
any potential workplace exposure within the initial two
weeks of employment.
M. Expert Witness. The Directorate of Technical Support will assist
Regional Offices and the States in locating expert witnesses. Expert
witnesses must be contacted before issuance of citations.
1. In the event that a 5(a)(1) citation is contested, proper expert
witness support will be required. Issues which the expert must
be prepared to address include:
a. The risk to workers associated with the exposure
circumstances.
b. Existence, feasibility and utility of abatement measures.
c. Recognition of the hazard in the industry.
2. Expert witnesses may also be necessary in other cases,
particularly those involving 29 CFR 1910.134.
N. Recording in the IMIS. A TB-related inspection is any health
inspection conducted to investigate the presence or alleged presence of
TB disease (i.e., a referral or complaint inspection).
1. When a TB-related inspection is conducted, complete the OSHA-1
as for any inspection and enter the code "N 02 TB" in Item 42,
Optional Information. EXAMPLE:
Type ID Value
N 2 TB
2. When an OSHA-7 is completed and the complaint alleges the presence
of TB hazards, enter the code "N 02 TB" in Item 46, Optional
Information.
3. When an OSHA-90 is completed and the referral alleges the presence
of TB hazards, enter the code "N 02 TB" in Item, 26, Optional
Information.
4. All IMIS case file data for TB-related inspections conducted since
October 1, 1990, shall be modified to include the appropriate TB
code.
O. Referrals
1. When a complaint or inquiry is received from a source in a state
plan regarding occupational exposure to TB, the Area Office shall
refer it to the state plan designee for action.
2. When a complaint or inquiry regarding occupational exposure to TB
in a state or local government health care facility is received in
a state without an OSHA-approved state plan, the Regional
Administrator shall refer it to the appropriate State public
health agency or local health agency.
P. Pre-citation Review. Citations proposed pursuant to this program
shall be reviewed prior to issuance, by the Regional Administrator and
Regional Office Solicitor for consistency with these procedures. The
Directorate of Technical Support shall be contacted to establish expert
witness support. The Office of Health Compliance Assistance shall be
provided with a copy of all citations issued related to TB during the
first 6 months of this directive.
Joseph A. Dear
Assistant Secretary
Distribution: National, Regional, and Area Offices
All Compliance Officers
State Designees
NIOSH Regional Program Directors
7(c)(1) Consultation Project Managers
Appendix No. A
October 28, 1994/Vol. 43/No.RR-13
MMWR Recommendations and Reports
MORBIDITY AND MORTALITY WEEKLY REPORT
----------------------------------------------------------------------------
Guidelines for preventing
the Transmission of
Mycobacterium Tuberculosis in
Health-Care Facilities, 1994
U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES
Public Health Service
Centers for Disease Control
and Prevention (CDC)
Atlanta, Georgia 30333
Contents
Executive Summary ...................................................1
I. Introduction ...................................................2
A. Purpose of Document .......................................2
B. Epidemiology, Transmission, and Pathogenesis of TB ........4
C. Risk for Nosocomial Transmission of M. tuberculosis .......5
D. Fundamentals of TB Infection Control ......................6
II. Recommendations ................................................8
A. Assignment of Responsibility ..............................8
B. Risk Assessment, Development of the TB
Infection-Control Plan, and Periodic Reassessment .........8
1. Risk assessment ......................................8
a. General .........................................8
b. Community TB profile ...........................17
c. Case surveillance ..............................17
d. Analysis of HCW PPD test screening data ........17
e. Review of TB patient medical records ...........18
f. Observation of TB infection-control
practices ......................................19
g. Engineering evaluation .........................19
2. Development of the TB Infection-Control Plan ........19
3. Periodic Reassessment ...............................19
4. Examples of Risk Assessment .........................22
C. Identifying, Evaluating, and Initiating Treatment
for Patients Who May Have Active TB ......................23
1. Identifying patients who may have active TB .........23
2. Diagnostic evaluation for active TB .................24
3. Initiation of treatment for suspected or
confirmed TB ........................................25
D. Management of Patients Who May Have Active TB in
Ambulatory-Care Settings and Emergency Departments .......25
E. Management of Hospitalized Patients Who Have
Confirmed or Suspected TB ................................27
1. Initiation of isolation for TB ......................27
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2. TB isolation practices ..............................28
3. The TB isolation room ...............................29
4. Discontinuation of TB isolation .....................30
5. Discharge planning ..................................31
F. Engineering Control Recommendations ......................31
1. General ventilation .................................31
2. Additional engineering control approaches ...........32
a. HEPA filtration ................................32
b. UVGI ...........................................32
G. Respiratory Protection ...................................33
H. Cough-inducing and Aerosol-Generating Procedures .........34
1. General guidelines ..................................34
2. Special considerations for bronchoscopy .............35
3. Special considerations for the administration
of aerosolized pentamidine ..........................35
I. Education and Training of HCWs ...........................36
J. HCW Counseling, Screening, and Evaluation ................37
1. Counseling HCWs regarding TB ........................37
2. Screening HCWs for active TB ........................38
3. Screening HCWs for latent TB infection ..............38
4. Evaluation and management of HCWs who have
positive PPD test results or active TB ..............40
a. Evaluation .....................................40
b. Routine and follow-up chest radiographs ........40
c. Workplace restrictions .........................41
1) Active TB .................................41
2) Latent TB infection .......................41
K. Problem Evaluation .......................................41
1. Investigating PPD test conversions and active
TB in HCWs ..........................................42
a. Investigating PPD test conversions in HCWs .....42
b. Investigating cases of active TB in HCWs .......47
2. Investigating possible patient-to-patient
transmission of M. tuberculosis .....................48
3. Investigating contacts of patients and HCWs
who have infectious TB ..............................48
L. Coordination with the Public Health Department ...........49
M. Additional Considerations for Selected Areas in
Health-Care Facilities and Other Health-Care
Settings .................................................50
1. Selected areas in health-care facilities ............50
a. Operating rooms ................................50
b. Autopsy rooms ..................................51
c. Laboratories ...................................51
2. Other health-care settings ..........................51
a. Emergency medical services .....................51
b. Hospices .......................................52
c. Long-term care facilities ......................52
d. Correctional facilities ........................52
e. Dental settings ................................52
f. Home-health-care settings ......................53
g. Medical offices ................................54
Supplement 1: Determining the Infectiousness of a TB Patient ......57
Supplement 2: Diagnosis and Treatment of Latent TB Infection
and Active TB ......................................................59
I. Diagnostic Procedures for TB Infection and Disease .......59
A. PPD Skin Testing and Anergy Testing .................59
1. Application and reading of PPD skin tests ......59
2. Interpretation of PPD skin tests ...............60
a. General ...................................60
b. HCWs ......................................61
3. Anergy testing .................................61
4. Pregnancy and PPD skin testing .................61
5. BCG vaccination and PPD skin testing ...........63
6. The booster phenomenon .........................63
B. Chest Radiography ...................................64
C. Bacteriology ........................................64
II. Preventive Therapy for Latent TB Infection and
Treatment of Active TB ...................................65
A. Preventive Therapy for Latent TB Infection ..........65
B. Treatment of Patients Who Have Active TB ............66
Supplement 3: Engineering Controls ................................69
I. Introduction .............................................69
II. Ventilation ..............................................69
A. Local Exhaust Ventilation ...........................70
1. Enclosing devices ..............................70
2. Exterior-devices ...............................71
3. Discharge exhaust from booths, tents,
and hoods ......................................71
B. General Ventilation .................................73
1. Dilution and removal ...........................73
a. Types of general ventilation systems ......73
b. Ventilation rates .........................74
2. Airflow patterns within rooms (air mixing) .....74
3. Airflow direction in the facility ..............76
a. Directional airflow .......................76
b. Negative pressure for achieving
directional airflow .......................76
4. Achieving negative pressure in a room ..........76
a. Pressure differential .....................76
b. Alternate methods for achieving
negative pressure .........................77
c. Monitoring negative pressure ..............78
C. HEPA filtration .....................................81
1. Use of HEPA filtration when exhausting air
to the outside .................................82
2. Recirculation of HEPA-filtered air to
other areas of a facility ......................82
3. Recirculation of HEPA-filtered air
within a room ..................................82
a. Fixed room-air recirculation systems ......84
b. Portable room-air recirculation units .....84
c. Evaluation of room-air recirculation
systems and units .........................85
4. Installing, maintaining, and monitoring
HEPA filters ...................................85
D. TB Isolation Rooms and Treatment Rooms ..............86
1. Preventing the escape of droplet nuclei
from the room ..................................87
2. Reducing the concentration of droplet
nuclei in the room .............................87
3. Exhaust from TB isolation rooms and
treatment rooms ................................87
4. Alternatives to TB isolation rooms .............87
III. UVGI ..........................................................88
A. Applications .............................................89
1. Duct irradiation ....................................89
2. Upper-room air irradiation ..........................89
B. Limitations ..............................................90
C. Safety Issues ............................................91
D. Exposure Criteria for UV Radiation .......................92
E. Maintenance and Monitoring ...............................93
1. Labeling and posting ................................93
2. Maintenance .........................................94
3. Monitoring ..........................................95
Supplement 4: Respiratory Protection ..............................97
I. Considerations for Selection of Respirators ................97
A. Performance Criteria for Personal Respirators
for Protection Against Transmission of M.
tuberculosis ........................................97
B. Specific Respirators ................................98
C. The Effectiveness of Respiratory Protective
Devices .............................................99
1. Face-seal leakage ..............................99
2. Filter leakage ................................100
3. Fit testing ...................................100
4. Fit checking ..................................101
5. Reuse of respirators ..........................101
II. Implementing a Personal Respiratory Protection Program .......102
Supplement 5: Decontamination-Cleaning, Disinfecting, and
Sterilizing of Patient-Care Equipment .............................105
References ........................................................106
Glossary ..........................................................113
Index .............................................................121
List of Tables ...............................................132
List of Figures ..............................................132
Acknowledgments
Drafts of this document have been reviewed by leaders of numerous medical,
scientific, public health, and labor organizations and others expert in
tuberculosis, acquired immunodeficiency syndrome, infection control,
hospital epidemiology, microbiology, ventilation, industrial hygiene,
nursing, dental practice, or emergency medical services. We thank the many
organizations and individuals for their thoughtful comments, suggestions,
and assistance.
TB Infection-Control Guidelines Work Group
Carmine J. Bozzi
Dale R. Burwen, M.D.
Samuel W. Dooley, M.D.
Patricia M. Simone, M.D.
National Center for Prevention Services
Consuelo Beck-Sague, M.D.
Elizabeth A. Bolyard, R.N., M.P.H.
William R. Jarvis, M.D.
National Center for Infectious Diseases
Philip J. Bierbaum
Christine A. Hudson, M.P.H.
Robert T. Hughes
Linda S. Martin, Ph.D.
Robert J. Mullan, M.D.
National Institute for Occupational Safety and Health
Brian M. Willis, J.D., M.P.H.
Office of the Director
Guidelines for Preventing
the Transmission of
Mycobacterium tuberculosis in
Health-Care Facilities, 1994
Executive Summary
This document updates and replaces all previously published guidelines for
the prevention of Mycobacterium tuberculosis transmission in health-care
facilities. The purpose of this revision is to emphasize the importance of
a) the hierarchy of control measures, including administrative and
engineering controls and personal respiratory protection; b) the use of
risk assessments for developing a written tuberculosis (TB) control plan;
c) early identification and management of persons who have TB; d) TB
screening programs for health-care workers (HCWs); e) HCW training and
education; and f) the evaluation of TB infection-control programs.
Transmission of M. tuberculosis is a recognized risk to patients and HCWs
in health-care facilities. Transmission is most likely to occur from
patients who have unrecognized pulmonary or laryngeal TB, are not on
effective anti-TB therapy, and have not been placed in TB isolation.
Several recent TB outbreaks in health-care facilities, including outbreaks
of multidrug-resistant TB, have heightened concern about nosocomial
transmission. Patients who have multidrug-resistant TB can remain
infectious for prolonged periods, which increases the risk for nosocomial
and/or occupational transmission of M. tuberculosis. Increases in the
incidence of TB have been observed in some geographic areas; these
increases are related partially to the high risk for TB among
immunosuppressed persons, particularly those infected with human
immunodeficiency virus (HIV). Transmission of M. tuberculosis to
HIV-infected persons is of particular concern because these persons are at
high risk for developing active TB if they become infected with the
bacteria. Thus, health-care facilities should be particularly alert to
the need for preventing transmission of M. tuberculosis in settings in
which HIV-infected persons work or receive care.
Supervisory responsibility for the TB infection-control program should be
assigned to a designated person or group of persons who should be given
the authority to implement and enforce TB infection-control policies. An
effective TB infection-control program requires early identification,
isolation, and treatment of persons who have active TB. The primary
emphasis of TB infection-control plans in health-care facilities should be
achieving these three goals by the application of a hierarchy of control
measures, including a) the use of administrative measures to reduce the
risk for exposure to persons who have infectious TB, b) the use of
engineering controls to prevent the spread and reduce the concentration of
infectious droplet nuclei, and c) the use of personal respiratory
protective equipment in areas where there is still a risk for exposure to
M. tuberculosis (e.g., TB isolation rooms). Implementation of a TB
infection-control program requires risk assessment and development of a TB
infection-control plan; early identification, treatment, and isolation of
infectious TB patients; effective engineering controls; an appropriate
respiratory protection program; HCW TB training, education, counseling,
and screening; and evaluation of the program's effectiveness.
Although completely eliminating the risk for transmission of M.
tuberculosis in all health-care facilities may not be possible at the
present time, adherence to these guidelines should reduce the risk to
persons in these settings. Recently, nosocomial TB outbreaks have
demonstrated the substantial morbidity and mortality among patients and
HCWs that have been associated with incomplete implementation of CDC's
Guidelines for Preventing the Transmission of Tuberculosis in Health-Care
Facilities, with Special Focus on HIV-Related Issues published in 1990.*
Follow-up investigations at some of these hospitals have documented that
complete implementation of measures similar or identical to those in the
1990 TB Guidelines significantly reduced or eliminated nosocomial
transmission of M. tuberculosis to patients and/or HCWs.
__________
* CDC. Guidelines for Preventing the Transmission of Tuberculosis in
Health-Care Facilities, with Special Focus on HIV-Related Issues. MMWR
1990;39(No. RR-17).
I. Introduction
A. Purpose of Document
In April 1992, the National MDR-TB Task Force published the
National Action Plan to Combat Multidrug-Resistant Tuberculosis
(1). The publication was a response to reported nosocomial
outbreaks of tuberculosis (TB), including outbreaks of
multidrug-resistant TB (MDR-TB), and the increasing incidence of
TB in some geographic areas. The plan called for the update and
revision of the guidelines for preventing nosocomial transmission
of Mycobacterium tuberculosis published December 7, 1990 (2).
Public meetings were held in October 1992 and January 1993 to
discuss revision of the 1990 TB Guidelines (2). CDC received
considerable input on various aspects of infection control,
including health-care worker (HCW) education; administrative
controls (e.g., having protocols for the early identification and
management of patients who have TB); the need for more specific
recommendations regarding ventilation; and clarification on the
use of respiratory protection in health-care settings. On the
basis of these events and the input received, on October 12,
1993, CDC published in the Federal Register the Draft Guidelines
For Preventing the Transmission of Tuberculosis in Health-Care
Facilities, Second Edition (3). During and after the 90-day
comment period following publication of this draft, CDC's TB
Infection-Control Guidelines Work Group received and reviewed
more than 2,500 comments.
The purpose of this document is to make recommendations for
reducing the risk for transmitting M. tuberculosis to HCWs,
patients, volunteers, visitors, and other persons in these
settings. The information also may serve as a useful resource for
educating HCWs about TB.
These recommendations update and replace all previously published
CDC recommendations for TB infection control in health-care
facilities (2,4). The recommendations in this document are
applicable primarily to inpatient facilities in which health care
is provided (e.g., hospitals, medical wards in correctional
facilities, nursing homes, and hospices). Recommendations
applicable to ambulatory-care facilities, emergency departments,
home-health-care settings, emergency medical services, medical
offices, dental settings, and other facilities or residential
settings that provide medical care are provided in separate
sections, with cross-references to other sections of the
guidelines if appropriate.
Designated personnel at health-care facilities should conduct a
risk assessment for the entire facility and for each area* and
occupational group, determine the risk for nosocomial or
occupational transmission of M. tuberculosis, and implement an
appropriate TB infection-control program. The extent of the TB
infection-control program may range from a simple program
emphasizing administrative controls in settings where there is
minimal risk for exposure to M. tuberculosis, to a comprehensive
program that includes administrative controls, engineering controls,
and respiratory protection in settings where the risk for exposure
is high. In all settings, administrative measures should be used to
minimize the number of HCWs exposed to M. tuberculosis while still
providing optimal care for TB patients. HCWs providing care to
patients who have TB should be informed about the level of risk for
transmission of M. tuberculosis and the appropriate control
measures to minimize that risk.
__________
* Area: a structural unit (e.g., a hospital ward or laboratory) or
functional unit (e.g., an internal medicine service) in which HCWs provide
services to and share air with a specific patient population or work with
clinical specimens that may contain viable M. tuberculosis organisms. The
risk for exposure to M. tuberculosis in a given area depends on the
prevalence of TB in the population served and the characteristics of the
environment.
In this document, the term "HCWs" refers to all the paid and
unpaid persons working in health-care settings who have the
potential for exposure to M. tuberculosis. This may include, but
is not limited to, physicians; nurses; aides; dental workers;
technicians; workers in laboratories and morgues; emergency
medical service (EMS) personnel; students; part-time personnel;
temporary staff not employed by the health-care facility; and
persons not involved directly in patient care but who are
potentially at risk for occupational exposure to M. tuberculosis
(e.g., volunteer workers and dietary, housekeeping, maintenance,
clerical, and janitorial staff).
Although the purpose of this document is to make recommendations
for reducing the risk for transmission of M. tuberculosis in
health-care facilities, the process of implementing these
recommendations must safeguard, in accordance with applicable
state and federal laws, the confidentiality and civil rights of
persons who have TB.
B. Epidemiology, Transmission, and Pathogenesis of TB
The prevalence of TB is not distributed evenly throughout all
segments of the U.S. population. Some subgroups or persons have a
higher risk for TB either because they are more likely than other
persons in the general population to have been exposed to and
infected with M. tuberculosis or because their infection is more
likely to progress to active TB after they have been infected (5).
In some cases, both of these factors may be present. Groups of
persons known to have a higher prevalence of TB infection include
contacts of persons who have active TB, foreign-born persons from
areas of the world with a high prevalence of TB (e.g., Asia, Africa,
the Caribbean, and Latin America), medically underserved populations
(e.g., some African-Americans, Hispanics, Asians and Pacific
Islanders, American Indians, and Alaskan Natives), homeless persons,
current or former correctional-facility inmates, alcoholics,
injecting-drug users, and the elderly. Groups with a higher risk
for progression from latent TB infection to active disease
include persons who have been infected recently (i.e., within the
previous 2 years), children less than 4 years of age, persons with
fibrotic lesions on chest radiographs, and persons with certain
medical conditions (i.e., human immunodeficiency virus [HIV]
infection, silicosis, gastrectomy or jejuno-ileal bypass, being
greater than or equal to 10% below ideal body weight, chronic renal
failure with renal dialysis, diabetes mellitus, immunosuppression
resulting from receipt of high-dose corticosteroid or other
immunosuppressive therapy, and some malignancies)(5).
M. tuberculosis is carried in airborne particles, or droplet
nuclei, that can be generated when persons who have pulmonary or
laryngeal TB sneeze, cough, speak, or sing (6). The particles are
an estimated 1-5 um in size, and normal air currents can keep them
airborne for prolonged time periods and spread them throughout a
room or building (7). Infection occurs when a susceptible person
inhales droplet nuclei containing M. tuberculosis, and these droplet
nuclei traverse the mouth or nasal passages, upper respiratory
tract, and bronchi to reach the alveoli of the lungs. Once in the
alveoli, the organisms are taken up by alveolar macrophages and
spread throughout the body. Usually within 2-10 weeks after initial
infection with M. tuberculosis, the immune response limits further
multiplication and spread of the tubercle bacilli; however, some
of the bacilli remain dormant and viable for many years. This
condition is referred to as latent TB infection. Persons with
latent TB infection usually have positive purified protein
derivative (PPD)-tuberculin skin-test results, but they do not
have symptoms of active TB, and they are not infectious.
In general, persons who become infected with M. tuberculosis have
approximately a 10% risk for developing active TB during their
lifetimes. This risk is greatest during the first 2 years after
infection. Immunocompromised persons have a greater risk for the
progression of latent TB infection to active TB disease; HIV
infection is the strongest known risk factor for this
progression. Persons with latent TB infection who become
coinfected with HIV have approximately an 8%-10% risk per year for
developing active TB (8). HIV-infected persons who are already
severely immunosuppressed and who become newly infected with M.
tuberculosis have an even greater risk for developing active TB
(9-12).
The probability that a person who is exposed to M. tuberculosis
will become infected depends primarily on the concentration of
infectious droplet nuclei in the air and the duration of exposure.
Characteristics of the TB patient that enhance transmission
include a) disease in the lungs, airways, or larynx; b) presence
of cough or other forceful expiratory measures; c) presence of
acid-fast bacilli (AFB) in the sputum; d) failure of the patient to
cover the mouth and nose when coughing or sneezing; e) presence of
cavitation on chest radiograph; f) inappropriate or short duration
of chemotherapy; and g) administration of procedures that can
induce coughing or cause aerosolization of M. tuberculosis (e.g.,
sputum induction). Environmental factors that enhance the
likelihood of transmission include a) exposure in relatively small,
enclosed spaces; b) inadequate local or general ventilation that
results in insufficient dilution and/or removal of infectious
droplet nuclei; and c) recirculation of air containing infectious
droplet nuclei. Characteristics of the persons exposed to M.
tuberculosis that may affect the risk for becoming infected are
not as well defined. In general, persons who have been infected
previously with M. tuberculosis may be less susceptible to
subsequent infection. However, reinfection can occur among
previously infected persons, especially if they are severely
immunocompromised. Vaccination with Bacille of Calmette and
Guerin (BCG) probably does not affect the risk for infection;
rather, it decreases the risk for progressing from latent TB
infection to active TB (13). Finally, although it is well
established that HIV infection increases the likelihood of
progressing from latent TB infection to active TB, it is unknown
whether HIV infection increases the risk for becoming infected if
exposed to M. tuberculosis.
C. Risk for Nosocomial Transmission of M. tuberculosis
Transmission of M. tuberculosis is a recognized risk in health-care
facilities (14-22). The magnitude of the risk varies considerably
by the type of health-care facility, the prevalence of TB in the
community, the patient population served, the HCW's occupational
group, the area of the health-care facility in which the HCW works,
and the effectiveness of TB infection-control interventions. The
risk may be higher in areas where patients with TB are provided
care before diagnosis and initiation of TB treatment and isolation
precautions (e.g., in clinic waiting areas and emergency
departments) or where diagnostic or treatment procedures that
stimulate coughing are performed. Nosocomial transmission of M.
tuberculosis has been associated with close contact with persons
who have infectious TB and with the performance of certain
procedures (e.g., bronchoscopy [17], endotracheal intubation and
suctioning [18], open abscess irrigation [20], and autopsy [21,22]).
Sputum induction and aerosol treatments that induce coughing may
also increase the potential for transmission of M. tuberculosis
(23,24). Personnel of health-care facilities should be particularly
alert to the need for preventing transmission of M. tuberculosis in
those facilities in which immunocompromised persons (e.g.,
HIV-infected persons) work or receive care -- especially if
cough-inducing procedures, such as sputum induction and aerosolized
pentamidine treatments, are being performed.
Several TB outbreaks among persons in health-care facilities have
been reported recently (11,24-28; CDC, unpublished data). Many of
these outbreaks involved transmission of multidrug-resistant strains
of M. tuberculosis to both patients and HCWs. Most of the patients
and some of the HCWs were HIV-infected persons in whom new infection
progressed rapidly to active disease. Mortality associated with
those outbreaks was high (range: 43%-93%). Furthermore, the interval
between diagnosis and death was brief (range of median intervals:
4-16 weeks). Factors contributing to these outbreaks included
delayed diagnosis of TB, delayed recognition of drug resistance,
and delayed initiation of effective therapy -- all of which
resulted in prolonged infectiousness, delayed initiation and
inadequate duration of TB isolation, inadequate ventilation in TB
isolation rooms, lapses in TB isolation practices and inadequate
precautions for cough-inducing procedures, and lack of adequate
respiratory protection. Analysis of data collected from three of
the health-care facilities involved in the outbreaks indicates that
transmission of M. tuberculosis decreased significantly or ceased
entirely in areas where measures similar to those in the 1990 TB
Guidelines were implemented (2,29-32). However, several interventions
were implemented simultaneously, and the effectiveness of the
separate interventions could not be determined.
D. Fundamentals of TB Infection Control
An effective TB infection-control program requires early
identification, isolation, and effective treatment of persons who
have active TB. The primary emphasis of the TB infection-control
plan should be on achieving these three goals. In all health-care
facilities, particularly those in which persons who are at high
risk for TB work of receive care, policies and procedures for TB
control should be developed, reviewed periodically, and evaluated
for effectiveness to determine the actions necessary to minimize
the risk for transmission of M. tuberculosis.
The TB infection-control program should be based on a hierarchy
of control measures. The first level of the hierarchy, and that
which affects the largest number of persons, is using
administrative measures intended primarily to reduce the risk for
exposing uninfected persons to persons who have infectious TB.
These measures include a) developing and implementing effective
written policies and protocols to ensure the rapid identification,
isolation, diagnostic evaluation, and treatment of persons likely
to have TB; b) implementing effective work practices among HCWs
in the health-care facility (e.g., correctly wearing respiratory
protection and keeping doors to isolation rooms closed); c)
educating, training, and counseling HCWs about TB; and d)
screening HCWs for TB infection and disease.
The second level of the hierarchy is the use of engineering
controls to prevent the spread and reduce the concentration of
infectious droplet nuclei. These controls include a) direct source
control using local exhaust ventilation, b) controlling direction
of airflow to prevent contamination of air in areas adjacent to the
infectious source, c) diluting and removing contaminated air via
general ventilation, and d) air cleaning via air filtration or
ultraviolet germicidal irradiation (UVGI).
The first two levels of the hierarchy minimize the number of
areas in the health-care facility where exposure to infectious TB
may occur, and they reduce, but do not eliminate, the risk in
those few areas where exposure to M. tuberculosis can still occur
(e.g., rooms in which patients with known or suspected infectious
TB are being isolated and treatment rooms in which cough-inducing
or aerosol-generating procedures are performed on such patients).
Because persons entering such rooms may be exposed to M.
tuberculosis, the third level of the hierarchy is the use of
personal respiratory protective equipment in these and certain
other situations in which the risk for infection with M.
tuberculosis may be relatively higher.
Specific measures to reduce the risk for transmission of M.
tuberculosis include the following:
* Assigning to specific persons in the health-care facility the
supervisory responsibility for designing, implementing,
evaluating, and maintaining the TB infection-control program
(Section II.A).
* Conducting a risk assessment to evaluate the risk for
transmission of M. tuberculosis in all areas of the
health-care facility, developing a written TB infection-control
program based on the risk assessment, and periodically
repeating the risk assessment to evaluate the effectiveness of
the TB infection-control program (Section II.B).
* Developing, implementing, and enforcing policies and protocols
to ensure early identification, diagnostic evaluation, and
effective treatment of patients who may have infectious TB
(Section II.C; Suppl. 2).
* Providing prompt triage for and appropriate management of
patients in the outpatient setting who may have infectious TB
(Section II.D).
* Promptly initiating and maintaining TB isolation for persons who
may have infectious TB and who are admitted to the inpatient
setting (Section II.E; Suppl. 1).
* Effectively planning arrangements for discharge (Section II.E).
* Developing, installing, maintaining, and evaluating
ventilation and other engineering controls to reduce the
potential for airborne exposure to M. tuberculosis (Section
II.F; Suppl. 3).
* Developing, implementing, maintaining, and evaluating a
respiratory protection program (Section II.G; Suppl. 4).
* Using precautions while performing cough-inducing procedures
(Section II.H; Suppl. 3).
* Educating and training HCWs about TB, effective methods for
preventing transmission of M. tuberculosis, and the benefits
of medical screening programs (Section II.I).
* Developing and implementing a program for routine periodic
counseling and screening of HCWs for active TB and latent TB
infection (Section II.J; Suppl. 2).
* Promptly evaluating possible episodes of M. tuberculosis
transmission in health-care facilities, including PPD skin-test
conversions among HCWs, epidemiologically associated cases
among HCWs or patients, and contacts of patients or HCWs who
have TB and who were not promptly identified and isolated
(Section II.K).
* Coordinating activities with the local public health department,
emphasizing reporting, and ensuring adequate discharge
follow-up and the continuation and completion of therapy
(Section II.L).
II. Recommendations
A. Assignment of Responsibility
* Supervisory responsibility for the TB infection-control program
should be assigned to a designated person or group of persons
with expertise in infection control, occupational health, and
engineering. These persons should be given the authority to
implement and enforce TB infection-control policies.
* If supervisory responsibility is assigned to a committee, one
person should be designated as the TB contact person.
Questions and problems can then be addressed to this person.
B. Risk Assessment, Development of the TB Infection-Control Plan,
and Periodic Reassessment
1. Risk assessment
a. General
* TB infection-control measures for each health-care
facility should be based on a careful assessment of
the risk for transmission of M. tuberculosis in that
particular setting. The first step in developing the
TB infection-control program should be to conduct a
baseline risk assessment to evaluate the risk for
transmission of M. tuberculosis in each area and
occupational group in the facility (Table 1, Figure 1).
Appropriate infection-control interventions can then be
developed on the basis of actual risk. Risk assessments
should be performed for all inpatient and outpatient
settings (e.g., medical and dental offices).
* Regardless of risk level, the management of patients
with known or suspected infectious TB should not vary.
However, the index of suspicion for infectious TB among
patients, the frequency of HCW PPD skin testing, the
number of TB isolation rooms, and other factors will
depend on whether the risk for transmission of M.
tuberculosis in the facility, area, or occupational group
is high, intermediate, low, very low, or minimal.
* The risk assessment should be conducted by a qualified
person or group of persons (e.g., hospital
epidemiologists, infectious disease specialists,
pulmonary disease specialists, infection-control
practitioners, health-care administrators, occupational
health personnel, engineers, HCWs, or local public
health personnel).
* The risk assessment should be conducted for the entire
facility and for specific areas within the facility
(e.g., medical, TB, pulmonary, or HIV wards; HIV,
infectious disease, or pulmonary clinics; and emergency
departments or other areas where TB patients might
receive care or where cough-inducing procedures are
performed). This should include both inpatient and
outpatient areas. In addition, risk assessments should
be conducted for groups of HCWs who work throughout the
facility rather than in a specific area (e.g.,
respiratory therapists; bronchoscopists; environmental
services, dietary, and maintenance personnel; and
students, interns, residents, and fellows).
TABLE 1. Elements of a risk assessment for tuberculosis (TB) in
health-care facilities
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1. Review the community TB profile (from public health department data).
2. Review the number of TB patients who were treated in each area of
area of the facility (both inpatient and outpatient). (This
information can be obtained by analyzing laboratory surveillance
data and by reviewing discharge diagnoses or medical and
infection-control records.)
3. Review the drug-susceptibility patterns of TB isolates of patients
who were treated at the facility.
4. Analyze purified protein derivative (PPD)-tuberculin skin-test
results of health-care workers (HCWs), by area or by occupational
group for HCWs not assigned to a specific area (e.g., respiratory
therapists).
5. To evaluate infection-control parameters, review medical records of
a sample of TB patients seen at the facility.
Calculate intervals from:
* admission until TB suspected;
* admission until TB evaluation performed;
* admission until acid-fast bacilli (AFB) specimens ordered;
* AFB specimens ordered until AFB specimens collected;
* AFB specimens collected until AFB smears performed and reported;
* AFB specimens collected until cultures performed and reported;
* AFB specimens collected until species identification conducted and
reported;
* AFB specimens collected until drug-susceptibility tests performed
and reported;
* admission until TB isolation initiated;
* admission until TB treatment initiated; and
* duration of TB isolation.
Obtain the following additional information:
* Were appropriate criteria used for discontinuing isolation?
* Did the patient have a history or prior admission to the facility
* Was the TB treatment regimen adequate?
* Were follow-up sputum specimens collected properly?
* Was appropriate discharge planning conducted?
6. Perform an observational review of TB infection control practices.
7. Review the most recent environmental evaluation and maintenance
procedures.
____________________________________________________________________________
(For Figure 1, see printed copy)
* Classification of risk for a facility, for a specific
area, and for a specific occupational group should be
based on a) the profile of TB in the community; b) the
number of infectious TB patients admitted to the
area or ward, or the estimated number of infectious TB
patients to whom HCWs in an occupational group may be
exposed; and c) the results of analysis of HCW PPD test
conversions (where applicable) and possible
person-to-person transmission of M. tuberculosis
(Figure 1).
* All TB infection-control programs should include periodic
reassessments of risk. The frequency of repeat risk
assessments should be based on the results of the most
recent risk assessment (Table 2, Figure 1).
* The "minimal-risk" category applies only to an entire
facility. A "minimal-risk" facility does not admit TB
patients to inpatient or outpatient areas and is not
located in a community with TB (i.e., counties or
communities in which TB cases have not been reported
during the previous year). Thus, there is essentially no
risk for exposure to TB patients in the facility. This
category may also apply to many outpatient settings
(e.g., many medical and dental offices).
(For Table 2, see printed copy)
* The "very low-risk" category generally applies only to an
entire facility. A very low-risk facility is one in which
a) patients with active TB are not admitted to inpatient
areas but may receive initial assessment and diagnostic
evaluation or outpatient management in outpatient areas
(e.g., ambulatory-care and emergency departments) and
b) patients who may have active TB and need inpatient
care are promptly referred to a collaborating facility.
In such facilities, the outpatient areas in which
exposure to patients with active TB could occur should be
assessed and assigned to the appropriate low-,
intermediate-, or high-risk category. Categorical
assignment will depend on the number of TB patients
examined in the area during the preceding year and
whether there is evidence of nosocomial transmission of M.
tuberculosis in the area. If TB cases have been reported
in the community, but no patients with active TB have
been examined in the outpatient area during the preceding
year, the area can be designated as very low risk (e.g.,
many medical offices).
The referring and receiving facilities should establish
a referral agreement to prevent inappropriate management
and potential loss to follow-up of patients suspected of
having TB during evaluation in the triage system of a
very low-risk facility.
In some facilities in which TB patients are admitted to
inpatient areas, a very low-risk protocol may be
appropriate for areas (e.g., administrative areas) or
occupational groups that have only a very remote
possibility of exposure to M. tuberculosis.
The very low-risk category may also be appropriate for
outpatient facilities that do not provide initial
assessment of persons who may have TB, but do screen
patients for active TB as part of a limited medical
screening before undertaking specialty care (e.g., dental
settings).
* Low-risk" areas or occupational groups are those in
which a) the PPD test conversion rate is not greater than
that for areas or groups in which occupational exposure
to M. tuberculosis is unlikely or than previous conversion
rates for the same area or group, b) no clusters* of PPD
test conversions have occurred, c) person-to-person
transmission of M. tuberculosis has not been detected,
and d) fewer than six TB patients are examined or
treated per year.
__________
* Cluster: two or more PPD skin-test conversions occurring within a
3-month period among HCWs in a specific area or occupational group, and
epidemiologic evidence suggests occupational (nosocomial) transmission.
* "Intermediate-risk" areas or occupational groups are
those in which a) the PPD test conversion rate is not
greater than that for areas or groups in which
occupational exposure to M. tuberculosis is unlikely or
than previous conversion rates for the same area or
group, b) no clusters of PPD test conversions have
occurred, c) person-to-person transmission of M.
tuberculosis has not been detected, and d) six or more
patients with active TB are examined or treated each
year. Survey data suggest that facilities in which six
or more TB patients are examined or treated each year
may have an increased risk for transmission of M.
tuberculosis (CDC, unpublished data); thus, areas in
which six or more patients with active TB are examined or
treated each year (or occupational groups in which HCWs
are likely to be exposed to six or more TB patients per
year) should be classified as "intermediate risk".
* "High-risk" areas or occupational groups are those in
which a) the PPD test conversion rate is significantly
greater than for areas or groups in which occupational
exposure to M. tuberculosis is unlikely or than previous
conversion rates for the same area or group, and
epidemiologic evaluation suggests nosocomial transmission;
or b) a cluster of PPD test conversions has occurred, and
epidemiologic evaluation suggests nosocomial transmission
of M. tuberculosis; or c) possible person-to-person
transmission of M. tuberculosis has been detected.
* If no data or insufficient data for adequate
determination of risk have been collected, such data
should be compiled, analyzed, and reviewed expeditiously.
b. Community TB profile
* A profile of TB in the community that is served by the
facility should be obtained from the public health
department. This profile should include, at a minimum,
the incidence (and prevalence, if available) of active
TB in the community and the drug-susceptibility
patterns of M. tuberculosis isolates (i.e., the
antituberculous agents to which each isolate is
susceptible and those to which it is resistant) from
patients in the community.
c. Case surveillance
* Data concerning the number of suspected and confirmed
active TB cases among patients and HCWs in the facility
should be systematically collected, reviewed, and used
to estimate the number of TB isolation rooms needed, to
recognize possible clusters of nosocomial transmission,
and to assess the level of potential occupational risk.
The number of TB patients in specific areas of a facility
can be obtained from laboratory surveillance data on
specimens positive for AFB smears or M. tuberculosis
cultures, from infection-control records, and from
databases containing information about hospital
discharge diagnoses.
* Drug-susceptibility patterns of M. tuberculosis
isolates from TB patients treated in the facility should
be reviewed to identify the frequency and patterns of
drug resistance. This information may indicate a need to
modify the initial treatment regimen or may suggest
possible nosocomial transmission or increased
occupational risk.
d. Analysis of HCW PPD test screening data
* Results of HCW PPD testing should be recorded in the
individual HCW's employee health record and in a
retrievable aggregate database of all HCW PPD test
results. Personal identifying information should be
handled confidentially. PPD test conversion rates
should be calculated at appropriate intervals to estimate
the risk for PPD test conversions for each area of the
facility and for each specific occupational group not
assigned to a specific area (Table 2). To calculate PPD
test conversion rates, the total number of previously
PPD-negative HCWs tested in each area or group (i.e.,
the denominator) and the number of PPD test
conversions among HCWs in each area or group (the
numerator) must be obtained.
* PPD test conversion rates for each area or occupational
group should be compared with rates for areas or groups
in which occupational exposure to M. tuberculosis is
unlikely and with previous conversion rates in the same
area or group to identify areas or groups where the
risk for occupational PPD test conversions may be
increased. A low number of HCWs in a specific area may
result in a greatly increased rate of conversion for that
area, although the actual risk may not be significantly
greater than that for other areas. Testing for statistical
significance (e.g., Fisher's exact test or chi square
test) may assist interpretation; however, lack of
statistical significance may not rule out a problem
(i.e., if the number of HCWs tested is low, there may
not be adequate statistical power to detect a
significant difference). Thus, interpretation of
individual situations is necessary.
* An epidemiologic investigation to evaluate the
likelihood of nosocomial transmission should be
conducted if PPD test conversions are noted (Section
II.K.1).
* The frequency and comprehensiveness of the HCW PPD
testing program should be evaluated periodically to
ensure that all HCWs who should be included in the
program are being tested at appropriate intervals. For
surveillance purposes, earlier detection of transmission
may be enhanced if HCWs in a given area or occupational
group are tested on different scheduled dates rather than
all being tested on the same date (Section II.J.3).
e. Review of TB patient medical records
* The medical records of a sample of TB patients examined
at the facility can be reviewed periodically to evaluate
infection-control parameters (Table 1). Parameters to
examine may include the intervals from date of admission
until a) TB was suspected, b) specimens for AFB smears
were ordered, c) these specimens were collected, d)
tests were performed, and e) results were reported.
Moreover, the adequacy of the TB treatment regimens that
were used should be evaluated.
* Medical record reviews should note previous hospital
admissions of TB patients before the onset of TB
symptoms. Patient-to-patient transmission may be
suspected if active TB occurs in a patient who had a
prior hospitalization during which exposure to another
TB patient occurred or if isolates from two or more TB
patients have identical characteristic drug-susceptibility
or DNA fingerprint patterns.
* Data from the case review should be used to determine if
there is a need to modify a) protocols for identifying
and isolating patients who may have infectious TB, b)
laboratory procedures, c) administrative policies and
practices, or d) protocols for patient management.
f. Observation of TB infection-control practices
* Assessing adherence to the policies of the TB
infection-control program should be part of the
evaluation process. This assessment should be performed
on a regular basis and whenever an increase occurs in
the number of TB patients or HCW PPD test conversions.
Areas at high risk for transmission of M. tuberculosis
should be monitored more frequently than other areas.
The review of patient medical records provides
information on HCW adherence to some of the policies of
the TB infection-control program. In addition, work
practices related to TB isolation (e.g., keeping doors to
isolation rooms closed) should be observed to determine if
employers are enforcing, and HCWs are adhering to, these
policies and if patient adherence is being enforced. If
these policies are not being enforced or adhered to,
appropriate education and other corrective action should
be implemented.
g. Engineering evaluation
* Results of engineering maintenance measures should be
reviewed at regular intervals (Table 3). Data from the
most recent evaluation and from maintenance procedures
and logs should be reviewed carefully as part of the
risk assessment.
2. Development of the TB Infection-Control Plan
* Based on the results of the risk assessment, a written TB
infection-control plan should be developed and implemented
for each area of the facility and for each occupational
group of HCWs not assigned to a specific area of the
facility (Table 2; Table 3).
* The occurrence of drug-resistant TB in the facility or the
community, or a relatively high prevalence of HIV infection
among patients or HCWs in the community, may increase the
concern about transmission of M. tuberculosis and may
influence the decision regarding which protocol to follow
(i.e., a higher-risk classification may be selected).
* Health-care facilities are likely to have a combination of
low-, intermediate-, and high-risk areas or occupational
groups during the same time period. The appropriate protocol
should be implemented for each area or group.
* Areas in which cough-inducing procedures are performed on
patients who may have active TB should, at the minimum,
implement the intermediate-risk protocol.
3. Periodic Reassessment
* Follow-up risk assessment should be performed at the
interval indicated by the most recent risk assessment
(Figure 1; Table 2). Based on the results of the follow-up
assessment, problem evaluation may need to be conducted or
the protocol may need to be modified to a higher- or
lower-risk level.
TABLE 3. Characteristics of an effective tuberculosis (TB)
infection-control program*
-----------------------------------------------------------------------------
I. Assignment of responsibility
A. Assign responsibility for the TB infection-control program to
qualified person(s).
B. Ensure that persons with expertise in infection control,
occupational health, and engineering are identified and included.
II. Risk assessment, TB infection-control plan, and periodic reassessment
A. Initial risk assessment
1. Obtain information concerning TB in the community.
2. Evaluate data concerning TB patients in the facility.
3. Evaluate data concerning pruified protein derivative
(PPD)-tuberculin skin-test conversions among health-care
workers (HCWs in the facility.
4. Rule out evidence of person-to-person transmission.
B. Written TB infection-control program
1. Select initial risk protocol(s).
2. Develop written TB infection-control protocols.
C. Repeat risk assessment at appropriate intervals.
1. Review current community and facility surveillance
data and PPD-tuberculin skin-test results.
2. Review records of TB patients.
3. Observe HCW infection-control practices.
4. Evaluate maintenance of engineering controls.
III. Identification, evaluation, and treatment of patients who have TB
A. Screen patients for signs and symptoms of active TB:
1. On initial encounter in emergency department or
ambulatory-care setting.
2. Before or at the time of admission.
B. Perform radiologic and bacteriologic evaluation of patients
who have signs and symptoms suggestive of TB.
C. Promptly initiate treatment.
IV. Managing outpatients who have possible infectious TB
A. Promptly initiate TB precautions.
B. Place patients in separate waiting areas or TB isolation
rooms.
C. Give patients a surgical mask, a box of tissues, and
instructions regarding the use of these items.
V. Managing inpatients who have possible infectious TB
A. Promptly isolate patients who have suspected or known
infectious TB.
B. Monitor the response to treatment.
C. Follow appropriate criteria for discontinuing isolation.
VI. Engineering recommendations
A. Design local exhaust and general ventilation in
collaboration with person who have expertise in ventilation
engineering.
B. Use a single-pass air systems or air recirculation after
high-efficiency particulate air (HEPA) filtration in areas
where infectious TB patients receive care.
C. Use additional measures, if needed, in areas where TB
patients may receive care.
D. Design TB isolation rooms in health-care facilities to achieve
greater than or equal to 6 air changes per hour (ACH) for existing
facilities and greater than or equal to 12 ACH for new or
renovated facilities.
E. Regularly monitor and maintain engineering controls.
F. TB isolation rooms that are being used should be monitored daily
to ensure they maintain negative pressure relative to the
hallways and all surrounding areas.
G. Exhaust TB isolation room air to outside or, if absolutely
unavoidable, recirculate after HEPA filtration.
VII. Respiratory protection
A. Respiratory protective devices should meet recommended performance
criteria.
B. Respiratory protection should be used by persons entering rooms in
which patients with known or suspected infectious TB are being
isolated, by HCWs when performing cough-inducing or
aerosol-generating procedures on such patients, and by persons in
other settings where administrative and engineering controls are
not likely to protect them from inhaling infectious airborne
droplet nuclei.
C. A respiratory protection program is required at all facilities in
which respiratory protection is used.
VII. Cough-inducing procedures
A. Do not perform such procedures on TB patients unless absolutely
necessary.
B. Perform such procedures in areas that have local exhaust
ventilation devices (e.g., booths or special enclosures) or, if
this is not feasible, in a room that meets the ventilation
requirements for TB isolation.
C. After completion of procedures, TB patients should remain in the
booth or special enclosure until their coughing subsides.
IX. HCW TB training and education
A. All HCWs should receive periodic TB education appropriate for
their work responsibilities and duties.
B. Training should include the epidemiology of TB in the facility.
C. TB education should emphasize concepts of the Pathogenesis of and
occupational risk for TB.
D. Training should describe work practices that reduce the likelihood
of transmitting M. tuberculosis.
X. HCW counseling and screening
A. Counsel all HCWs regarding TB and TB infection.
B. Counsel all HCWs about the increased risk to immunocompromised
persons for developed active TB.
C. Perform PPD skin tests on HCWs at the beginning of their employment,
and repeat PPD tests at periodic intervals.
D. Evaluate symptomatic HCWs for active TB.
XI. Evaluate HCW PPD test conversions and possible nosocomial
transmission of M. tuberculosis.
XII. Coordinate efforts with public health department(s)
-----------------------------------------------------------------------------
* A program such as this is appropriate for health-care facilities in
which there is a high risk for transmission of Mycobacterium
tuberculosis.
* After each risk assessment, the staff responsible for TB
control, in conjunction with other appropriate HCWs, should
review all TB control policies to ensure that they are
effective and meet current needs.
4. Examples of Risk Assessment
Examples of six hypothetical situations and the means by which
surveillance data are used to select a TB control protocol are
described as follows:
Hospital A. The overall HCW PPD test conversion rate in the
facility is 1.6%. No areas or HCW occupational groups have
a significantly greater PPD test conversion rate than areas
or groups in which occupational exposure to M. tuberculosis
is unlikely (or than previous rates for the same area or
group). No clusters of PPD test conversions have occurred.
Patient-to-patient transmission has not been detected.
Patients who have TB are admitted to the facility, but no
area admits six or more TB patients per year. The low-risk
protocol will be followed in all areas.
Hospital B. The overall HCW PPD test conversion rate in the
facility is 1.8%. The PPD test conversion rate for the
medical intensive-care unit rate is significantly higher
than all other areas in the facility. The problem
identification process is initiated (Section II.K). It is
determined that all TB patients have been isolated
appropriately. Other potential problems are then evaluated,
and the cause for the higher rate is not identified. After
consulting the public health department TB
infection-control program, the high-risk protocol is
followed in the unit until the PPD test conversion rate is
similar to areas of the facility in which occupational
exposure to TB patients is unlikely. If the rate remains
significantly higher than other areas, further evaluation,
including environmental and procedural studies, will be
performed to identify possible reasons for the high
conversion rate.
Hospital C. The overall HCW PPD test conversion rate in the
facility is 2.4%. Rates range from 0 to 2.6% for the
individual areas and occupational groups. None of these
rates is significantly higher than rates for areas in which
occupational exposure to M. tuberculosis is unlikely. No
particular HCW group has higher conversion rates than the
other groups. No clusters of HCW PPD test conversions have
occurred. In two of the areas, HCWs cared for more than six
TB patients during the preceding year. These two areas will
follow the intermediate-risk protocol, and all other areas
will follow the low-risk protocol. This hospital is located
in the southeastern United States, and these conversion
rates may reflect cross-reactivity with nontuberculous
mycobacteria.
Hospital D. The overall HCW PPD test conversion rate in the
facility is 1.2%. In no area did HCWs care for six or more
TB patients during the preceding year. Three of the 20
respiratory therapists tested had PPD conversions, for a
rate of 15%. The respiratory therapists who had PPD test
conversions had spent all or part of their time in the
pulmonary function laboratory, where induced sputum
specimens were obtained. A low-risk protocol is maintained
for all areas and occupational groups in the facility
except for respiratory therapists. A problem evaluation is
conducted in the pulmonary function laboratory (Section
II.K). It is determined that the ventilation in this area
is inadequate. Booths are installed for sputum induction.
PPD testing and the risk assessment are repeated 3 months
later. If the repeat testing at 3 months indicates that no
more conversions have occurred, the respiratory therapists
will return to the low-risk protocol.
Hospital E. Hospital E is located in a community that has a
relatively low incidence of TB. To optimize TB services in the
community, the four hospitals in the community have developed an
agreement that one of them (e.g., Hospital G) will provide all
inpatient services to persons who have suspected or confirmed
TB. The other hospitals have implemented protocols in their
ambulatory-care clinics and emergency departments to identify
patients who may have active TB. These patients are then
transferred to Hospital G for inpatient care if such care is
considered necessary. After discharge from Hospital G, they
receive follow-up care in the public health department's TB
clinic. During the preceding year, Hospital E has identified
fewer than six TB patients in its ambulatory-care and emergency
departments and has had no PPD test conversions or other
evidence of M. tuberculosis transmission among HCWs or patients
in these areas. These areas are classified as low risk, and all
other areas are classified as very low risk.
Hospital F. Hospital F is located in a county in which no TB
cases have been reported during the preceding 2 years. A risk
assessment conducted at the facility did not identify any
patients who had suspected or confirmed TB during the preceding
year. The facility is classified as minimal risk.
C. Identifying, Evaluating, and Initiating Treatment for Patients
Who May Have Active TB
The most important factors in preventing transmission of M.
tuberculosis are the early identification of patients who may have
infectious TB, prompt implementation of TB precautions for such
patients, and prompt initiation of effective treatment for those
who are likely to have TB.
1. Identifying patients who may have active TB
* Health-care personnel who are assigned responsibility for TB
infection control in ambulatory-care and inpatient settings
should develop, implement, and enforce protocols for the
early identification of patients who may have infectious TB.
* The criteria used in these protocols should be based on the
prevalence and characteristics of TB in the population
served by the specific facility. These protocols should be
evaluated periodically and revised according to the results
of the evaluation. Review of medical records of patients who
were examined in the facility and diagnosed as having TB
may serve as a guide for developing or revising these
protocols.
* A diagnosis of TB may be considered for any patient who has
a persistent cough (i.e., a cough lasting for greater than
or equal to 3 weeks) or other signs or symptoms compatible
with active TB (e.g., bloody sputum, night sweats, weight
loss, anorexia, or fever). However, the index of suspicion
for TB will vary in different geographic areas and will
depend on the prevalence of TB and other characteristics
of the population served by the facility. The index of
suspicion for TB should be very high in geographic areas or
among groups of patients in which the prevalence of TB is
high (Section I.B). Appropriate diagnostic measures should
be conducted and TB precautions implemented for patients
in whom active TB is suspected.
2. Diagnostic evaluation for active TB
* Diagnostic measures for identifying TB should be conducted
for patients in whom active TB is being considered. These
measures include obtaining a medical history and performing
a physical examination, PPD skin test, chest radiograph, and
microscopic examination and culture of sputum or other
appropriate specimens (6,34,35). Other diagnostic procedures
(e.g., bronchoscopy or biopsy) may be indicated for some
patients (36,37).
* Prompt laboratory results are crucial to the proper
treatment of the TB patient and to early initiation of
infection control. To ensure timely results, laboratories
performing mycobacteriologic tests should be proficient at
both the laboratory and administrative aspects of specimen
processing. Laboratories should use the most rapid methods
available (e.g., fluorescent microscopy for AFB smears;
radiometric culture methods for isolation of mycobacteria;
p-nitro-a-acetylamino-b-hydroxy-proprophenone [NAP] test,
nucleic acid probes, or high-pressure liquid chromatography
[HPLC] for species identification; and radiometric methods
for drug-susceptibility testing). As other more rapid or
sensitive tests become available, practical, and affordable,
such tests should be incorporated promptly into the
mycobacteriology laboratory. Laboratories that rarely
receive specimens for mycobacteriologic analysis should
refer the specimens to a laboratory that more frequently
performs these tests.
* Results of AFB sputum smears should be available within 24
hours of specimen collection (38).
* The probability of TB is greater among patients who have
positive PPD test results or a history of positive PPD
test results, who have previously had TB or have been
exposed to M. tuberculosis, or who belong to a group at
high risk for TB (Section I.B). Active TB is strongly
suggested if the diagnostic evaluation reveals AFB in
sputum, a chest radiograph suggestive of TB, or symptoms
highly suggestive of TB. TB can occur simultaneously in
immunosuppressed persons who have pulmonary infections
caused by other organisms (e.g., Pneumocystis carinii or
Mycobacterium avium complex) and should be considered in the
diagnostic evaluation of all patients who have symptoms
compatible with TB (Suppl. 1; Suppl. 2).
* TB may be more difficult to diagnose among persons who
have HIV infection (or other conditions associated with
severe suppression of cell-mediated immunity) because of
a nonclassical clinical or radiographic presentation and/or
the simultaneous occurrence of other pulmonary infections
(e.g., P. carinii pneumonia and M. avium complex). The
difficulty in diagnosing TB in HIV-infected persons may be
further compounded by impaired responses to PPD skin tests
(39,40), the possibly lower sensitivity of sputum smears
for detecting AFB (41), or the overgrowth of cultures with
M. avium complex in specimens from patients infected with
both M. avium complex and M. tuberculosis (42).
* Immunosuppressed patients who have pulmonary signs or
symptoms that are ascribed initially to infections or
conditions other than TB should be evaluated initially for
coexisting TB. The evaluation for TB should be repeated if
the patient does not respond to appropriate therapy for
the presumed cause(s) of the pulmonary abnormalities (Suppl.
1; Suppl. 2).
* Patients with suspected or confirmed TB should be reported
immediately to the appropriate public health department so
that standard procedures for identifying and evaluating TB
contacts can be initiated.
3. Initiation of treatment for suspected or confirmed TB
* Patients who have confirmed active TB or who are
considered highly likely to have active TB should be
started promptly on appropriate treatment in accordance
with current guidelines (Suppl. 2)(43). In geographic
areas or facilities that have a high prevalence of MDR-TB,
the initial regimen used may need to be enhanced while the
results of drug-susceptibility tests are pending. The
decision should be based on analysis of surveillance data.
* While the patient is in the health-care facility, anti-TB
drugs should be administered by directly observed therapy
(DOT), the process by which an HCW observes the patient
swallowing the medications. Continuing DOT after the
patient is discharged should be strongly considered. This
decision and the arrangements for providing outpatient
DOT should be made in collaboration with the public health
department.
D. Management of Patients Who May Have Active TB in Ambulatory-Care
Settings and Emergency Departments
* Triage of patients in ambulatory-care settings and emergency
departments should include vigorous efforts to promptly identify
patients who have active TB. HCWs who are the first points of
contact in facilities that serve populations at risk for TB
should be trained to ask questions that will facilitate
identification of patients with signs and symptoms suggestive
of TB.
* Patients with signs or symptoms suggestive of TB should be
evaluated promptly to minimize the amount of time they are in
ambulatory-care areas. TB precautions should be followed while
the diagnostic evaluation is being conducted for these patients.
* TB precautions in the ambulatory-care setting should include a)
placing these patients in a separate area apart from other
patients, and not in open waiting areas (ideally, in a room or
enclosure meeting TB isolation requirements); b) giving these
patients surgical masks* to wear and instructing them to keep
their masks on; and c) giving these patients tissues and
instructing them to cover their mouths and noses with the
tissues when coughing or sneezing.
__________
* Surgical masks are designed to prevent the respiratory secretions of
the person wearing the mask from entering the air. When not in a TB
isolation room, patients suspected of having TB should wear surgical masks
to reduce the expulsion of droplet nuclei into the air. These patients do
not need to wear particulate respirators, which are designed to filter the
air before it is inhaled by the person wearing the mask. Patients suspected
of having or known to have TB should never wear a respirator that has an
exhalation valve, because the device would provide no barrier to the
expulsion of droplet nuclei into the air.
* TB precautions should be followed for patients who are known to
have active TB and who have not completed therapy until a
determination has been made that they are noninfectious
(Suppl. 1).
* Patients with active TB who need to attend a health-care clinic
should have appointments scheduled to avoid exposing
HIV-infected or otherwise severely immunocompromised persons to
M. tuberculosis. This recommendation could be accomplished by
designating certain times of the day for appointments for these
patients or by treating them in areas where immunocompromised
persons are not treated.
* Ventilation in ambulatory-care areas where patients at high risk
for TB are treated should be designed and maintained to reduce
the risk for transmission of M. tuberculosis. General-use areas
(e.g., waiting rooms) and special areas (e.g., treatment or TB
isolation rooms in ambulatory areas) should be ventilated in
the same manner as described for similar inpatient areas
(Sections II.E.3, II.F; Suppl. 3). Enhanced general ventilation
or the use of air-disinfection techniques (e.g., UVGI or
recirculation of air within the room through high-efficiency
particulate air [HEPA] filters) may be useful in general-use
areas of facilities where many infectious TB patients receive
care (Section II.F; Suppl. 3).
* Ideally, ambulatory-care settings in which patients with TB are
frequently examined or treated should have a TB isolation room(s)
available. Such rooms are not necessary in ambulatory-care
settings in which patients who have confirmed or suspected TB
are seen infrequently. However, these facilities should have a
written protocol for early identification of patients with TB
symptoms and referral to an area or a collaborating facility
where the patient can be evaluated and managed appropriately.
These protocols should be reviewed on a regular basis and
revised as necessary. The additional guidelines in Section II.H
should be followed in ambulatory-care settings where
cough-inducing procedures are performed on patients who may
have active TB.
E. Management of Hospitalized Patients Who Have Confirmed or
Suspected TB
1. Initiation of isolation for TB
* In hospitals and other inpatient facilities, any patient
suspected of having or known to have infectious TB should
be placed in a TB isolation room that has currently
recommended ventilation characteristics (Section II.E.3;
Suppl. 3). Written policies for initiating isolation should
specify a) the indications for isolation, b) the person(s)
authorized to initiate and discontinue isolation, c) the
isolation practices to follow, d) the monitoring of
isolation, e) the management of patients who do not adhere
to isolation practices, and f) the criteria for
discontinuing isolation.
* In rare circumstances, placing more than one TB patient
together in the same room may be acceptable. This practice
is sometimes referred to as "cohorting" Because of the risk
for patients becoming superinfected with drug-resistant
organisms, patients with TB should be placed in the same
room only if all patients involved a) have culture-confirmed
TB, b) have drug-susceptibility test results available on a
current specimen obtained during the present hospitalization,
c) have identical drug-susceptibility patterns on these
specimens, and d) are on effective therapy. Having isolates
with identical DNA fingerprint patterns is not adequate
evidence for placing two TB patients together in the same
room, because isolates with the same DNA fingerprint pattern
can have different drug-susceptibility patterns.
* Pediatric patients with suspected or confirmed TB should be
evaluated for potential infectiousness according to the
same criteria as are adults (i.e., on the basis of
symptoms, sputum AFB smears, radiologic findings, and other
criteria) (Suppl. 1). Children who may be infectious should
be placed in isolation until they are determined to be
noninfectious. Pediatric patients who may be infectious
include those who have laryngeal or extensive pulmonary
involvement, pronounced cough, positive sputum AFB smears,
or cavitary TB or those for whom cough-inducing procedures
are performed (44).
* The source of infection for a child with TB is often a
member of the child's family (45). Therefore, parents and
other visitors of all pediatric TB patients should be
evaluated for TB as soon as possible. Until they have been
evaluated, or the source case is identified, they should
wear surgical masks when in areas of the facility outside
of the child's room, and they should refrain from visiting
common areas in the facility (e.g., the cafeteria or
lounge areas).
* TB patients in intensive-care units should be treated the
same as patients in noncritical-care settings. They should
be placed in TB isolation and have respiratory secretions
submitted for AFB smear and culture if they have
undiagnosed pulmonary symptoms suggestive of TB.
* If readmitted to a health-care facility, patients who are
known to have active TB and who have not completed therapy
should have TB precautions applied until a determination
has been made that they are noninfectious (Suppl. 1).
2. TB isolation practices
* Patients who are placed in TB isolation should be educated
about the mechanisms of M. tuberculosis transmission and
the reasons for their being placed in isolation. They
should be taught to cover their mouths and noses with a
tissue when coughing or sneezing, even while in the
isolation room, to contain liquid drops and droplets before
they are expelled into the air (46).
* Efforts should be made to facilitate patient adherence to
isolation measures (e.g., staying in the TB isolation room).
Such efforts might include the use of incentives (e.g.,
providing them with telephones, televisions, or radios in
their rooms or allowing special dietary requests). Efforts
should also be made to address other problems that could
interfere with adherence to isolation (e.g., management of
the patient's withdrawal from addictive substances
[including tobacco]).
* Patients placed in isolation should remain in their
isolation rooms with the door closed. If possible,
diagnostic and treatment procedures should be performed in
the isolation rooms to avoid transporting patients through
other areas of the facility. If patients who may have
infectious TB must be transported outside their isolation
rooms for medically essential procedures that cannot be
performed in the isolation rooms, they should wear surgical
masks that cover their mouths and noses during transport.
Persons transporting the patients do not need to wear
respiratory protection outside the TB isolation rooms.
Procedures for these patients should be scheduled at
times when they can be performed rapidly and when waiting
areas are less crowded.
* Treatment and procedure rooms in which patients who have
infectious TB or who have an undiagnosed pulmonary disease
and are at high risk for active TB receive care should meet
the ventilation recommendations for isolation rooms (Section
II.E.3; Suppl. 3). Ideally, facilities in which TB patients
are frequently treated should have an area in the radiology
department that is ventilated separately for TB patients. If
this is not possible, TB patients should wear surgical
masks and should stay in the radiology suite the minimum
amount of time possible, then be returned promptly to their
isolation rooms.
* The number of persons entering an isolation room should be
minimal. All persons who enter an isolation room should wear
respiratory protection (Section II.G; Suppl. 4). The
patient's visitors should be given respirators to wear
while in the isolation room, and they should be given
general instructions on how to use their respirators.
* Disposable items contaminated with respiratory secretions
are not associated with transmission of M. tuberculosis.
However, for general infection-control purposes, these
items should be handled and transported in a manner that
reduces the risk for transmitting other microorganisms to
patients, HCWs, and visitors and that decreases
environmental contamination in the health-care facility.
Such items should be disposed of in accordance with
hospital policy and applicable regulations (Suppl. 5).
3. The TB isolation room
* TB isolation rooms should be single-patient rooms with
special ventilation characteristics appropriate for the
purposes of isolation (Suppl. 3). The primary purposes of
TB isolation rooms are to a) separate patients who are
likely to have infectious TB from other persons; b) provide
an environment that will allow reduction of the
concentration of droplet nuclei through various
engineering methods; and c) prevent the escape of droplet
nuclei from the TB isolation room and treatment room, thus
preventing entry of M. tuberculosis into the corridor and
other areas of the facility.
* To prevent the escape of droplet nuclei, the TB isolation
room should be maintained under negative pressure (Suppl.
3). Doors to isolation rooms should be kept closed, except
when patients or personnel must enter or exit the room, so
that negative pressure can be maintained.
* Negative pressure in the room should be monitored daily
while the room is being used for TB isolation.
* The American Society of Heating, Refrigerating and
Air-Conditioning Engineers, Inc. (ASHRAE) (47), the
American Institute of Architects (AIA) (48), and the Health
Resources and Services Administration (49) recommend a
minimum of 6 air changes per hour (ACH) for TB isolation
and treatment rooms. This ventilation rate is based on
comfort and odor control considerations. The effectiveness
of this level of airflow in reducing the concentration of
droplet nuclei in the room, thus reducing the transmission
of airborne pathogens, has not been evaluated directly or
adequately.
Ventilation rates of greater than 6 ACH are likely to
produce an incrementally greater reduction in the
concentration of bacteria in a room than are lower rates
(50-52). However, accurate quantitation of decreases in
risk that would result from specific increases in
general ventilation levels has not been performed and may
not be possible.
For the purposes of reducing the concentration of droplet
nuclei, TB isolation and treatment rooms in existing
health-care facilities should have an airflow of greater
than or equal to 6 ACH. Where feasible, this airflow rate
should be increased to greater than or equal to 12 ACH by
adjusting or modifying the ventilation system or by using
auxiliary means (e.g., recirculation of air through fixed
HEPA filtration systems or portable air cleaners) (Suppl.
3, Section II.B.5.a) (53). New construction or renovation
of existing health-care facilities should be designed so
that TB isolation rooms achieve an airflow of greater than
or equal to 12 ACH.
* Air from TB isolation rooms and treatment rooms used to
treat patients who have known or suspected infectious TB
should be exhausted to the outside in accordance with
applicable federal, state, and local regulations. The air
should not be recirculated into the general ventilation.
In some instances, recirculation of air into the general
ventilation system from such rooms is unavoidable (i.e.,
in existing facilities in which the ventilation system or
facility configuration makes venting the exhaust to the
outside impossible). In such cases, HEPA filters should be
installed in the exhaust duct leading from the room to the
general ventilation system to remove infectious organisms
and particulates the size of droplet nuclei from the air
before it is returned to the general ventilation system
(Section II.F; Suppl. 3). Air from TB isolation and
treatment rooms in new or renovated facilities should not
be recirculated into the general ventilation system.
* Although not required, an anteroom may increase the
effectiveness of the isolation room by minimizing the
potential escape of droplet nuclei into the corridor when
the door is opened. To work effectively, the anteroom should
have positive air pressure in relation to the isolation
room. The pressure relationship between the anteroom and the
corridor may vary according to ventilation design.
* Upper-room air UVGI may be used as an adjunct to general
ventilation in the isolation room (Section II.F; Suppl.
3). Air in the isolation room may be recirculated within
the room through HEPA filters or UVGI devices to increase
the effective ACH and to increase thermal efficiency.
* Health-care facilities should have enough isolation rooms
to appropriately isolate all patients who have suspected
or confirmed active TB. This number should be estimated
using the results of the risk assessment of the health-care
facility. Except for minimal- and very low-risk health-care
facilities, all acute-care inpatient facilities should have
at least one TB isolation room (Section II.B).
* Grouping isolation rooms together in one area of the
facility may reduce the possibility of transmitting M.
tuberculosis to other patients and may facilitate care of
TB patients and the installation and maintenance of optimal
engineering (particularly ventilation) controls.
4. Discontinuation of TB isolation
* TB isolation can be discontinued if the diagnosis of TB
is ruled out. For some patients, TB can be ruled out when
another diagnosis is confirmed. If a diagnosis of TB cannot
be ruled out, the patient should remain in isolation until
a determination has been made that the patient is
noninfectious. However, patients can be discharged from the
healthcare facility while still potentially infectious if
appropriate postdischarge arrangements can be ensured
(Section II.E.5).
* The length of time required for a TB patient to become
noninfectious after starting anti-TB therapy varies
considerably (Suppl. 1). Isolation should be discontinued
only when the patient is on effective therapy, is improving
clinically, and has had three consecutive negative sputum
AFB smears collected on different days.
* Hospitalized patients who have active TB should be
monitored for relapse by having sputum AFB smears examined
regularly (e.g., every 2 weeks). Nonadherence to therapy
(i.e., failure to take medications as prescribed) and the
presence of drug-resistant organisms are the two most
common reasons why patients remain infectious despite
treatment. These reasons should be considered if a patient
does not respond clinically to therapy within 2-3 weeks.
* Continued isolation throughout the hospitalization should
be strongly considered for patients who have MDR-TB because
of the tendency for treatment failure or relapse (i.e.,
difficulty in maintaining noninfectiousness) that has been
observed in such cases.
5. Discharge planning
* Before a TB patient is discharged from the health-care
facility, the facility's staff and public health
authorities should collaborate to ensure continuation of
therapy. Discharge planning in the health-care facility
should include, at a minimum, a) a confirmed outpatient
appointment with the provider who will manage the patient
until the patient is cured, b) sufficient medication to take
until the outpatient appointment, and c) placement into case
management (e.g., DOT) or outreach programs of the public
health department. These plans should be initiated and in
place before the patient's discharge.
* Patients who may be infectious at the time of discharge
should only be discharged to facilities that have isolation
capability or to their homes. Plans for discharging a
patient who will return home must consider whether all the
household members were infected previously and whether any
uninfected household members are at very high risk for
active TB if infected (e.g., children less than 4 years of
age or persons infected with HIV or otherwise severely
immunocompromised). If the household does include such
persons, arrangements should be made to prevent them from
being exposed to the TB patient until a determination
has been made that the patient is noninfectious.
F. Engineering Control Recommendations
1. General ventilation
This section deals only with engineering controls for
general-use areas of health-care facilities (e.g., waiting-room
areas and emergency departments). Recommendations for
engineering controls for specific areas of the facility (e.g.,
TB isolation rooms) are contained in the sections encompassing
those areas. Details regarding ventilation design, evaluation,
and supplemental approaches are described in Supplement 3.
* Health-care facilities should either a) include as part of
their staff an engineer or other professional with expertise
in ventilation or b) have this expertise available from a
consultant who is an expert in ventilation engineering and
who also has hospital experience. These persons should work
closely with infection-control staff to assist in
controlling airborne infections.
* Ventilation system designs in health-care facilities should
meet any applicable federal, state, and local requirements.
* The direction of airflow in health-care facilities should
be designed, constructed, and maintained so that air flows
from clean areas to less-clean areas.
* Health-care facilities serving populations that have a high
prevalence of TB may need to supplement the general
ventilation or use additional engineering approaches (i.e.,
HEPA filtration or UVGI) in general-use areas where TB
patients are likely to go (e.g., waiting-room areas,
emergency departments, and radiology suites). A single-pass,
nonrecirculating system that exhausts air to the outside, a
recirculation system that passes air through HEPA filters
before recirculating it to the general ventilation system,
or upper air UVGI may be used in such areas.
2. Additional engineering control approaches
a. HEPA filtration
HEPA filters may be used in a number of ways to reduce or
eliminate infectious droplet nuclei from room air or
exhaust (Suppl. 3). These methods include placement of HEPA
filters a) in exhaust ducts discharging air from booths or
enclosures into the surrounding room; b) in ducts or in
ceiling- or wall-mounted units, for recirculation of air
within an individual room (fixed recirculation systems); c)
in portable air cleaners; d) in exhaust ducts to remove
droplet nuclei from air being discharged to the outside,
either directly or through ventilation equipment; and e)
in ducts discharging air from the TB isolation room into
the general ventilation system. In any application, HEPA
filters should be installed carefully and maintained
meticulously to ensure adequate functioning.
The manufacturers of in-room air cleaning equipment
should provide documentation of the HEPA filter efficiency
and the efficiency of the device in lowering room air
contaminant levels.
b. UVGI
For general-use areas in which the risk for transmission of
M. tuberculosis is relatively high, UVGI lamps may be used
as an adjunct to ventilation for reducing the concentration
of infectious droplet nuclei (Suppl. 3), although the
effectiveness of such units has not been evaluated
adequately. Ultra-violet (UV) units can be installed in a
room or corridor to irradiate the air in the upper portion
of the room (i.e., upper-room air irradiation), or they can
be installed in ducts to irradiate air passing through the
ducts. UV units installed in ducts should not be
substituted for HEPA filters in ducts that discharge air
from TB isolation rooms into the general ventilation
system. However, UV units can be used in ducts that
recirculate air back into the same room.
To function properly and decrease hazards to HCWs and
others in the health-care facility, UV lamps should be
installed properly and maintained adequately, which
includes the monitoring of irradiance levels. UV tubes
should be changed according to the manufacturer's
instructions or when meter readings indicate tube failure.
An employee trained in the use and handling of UV lamps
should be responsible for these measures and for keeping
maintenance records. Applicable safety guidelines should
be followed. Caution should be exercised to protect HCWs,
patients, visitors, and others from excessive exposure to
UV radiation.
G. Respiratory Protection
* Personal respiratory protection should be used by a) persons
entering rooms in which patients with known or suspected
infectious TB are being isolated, b) persons present during
cough-inducing or aerosol-generating procedures performed on
such patients, and c) persons in other settings where
administrative and engineering controls are not likely to
protect them from inhaling infectious airborne droplet nuclei
(Suppl. 4). These other settings include transporting patients
who may have infectious TB in emergency transport vehicles and
providing urgent surgical or dental care to patients who may
have infectious TB before a determination has been made that
the patient is noninfectious (Suppl. 1).
* Respiratory protective devices used in health-care settings for
protection against M. tuberculosis should meet the following
standard performance criteria:
1. The ability to filter particles 1 um in size in the unloaded*
state with a filter efficiency of greater than or equal to 95%
(i.e., filter leakage of less than or equal to 5%), given flow
rates of up to 50 L per minute.
__________
* Some filters become more efficient as they become loaded with dust.
Health-care settings do not have enough dust in the air to load a filter on
a respirator. Therefore, the filter efficiency for respirators used in
health-care settings must be determined in the unloaded state.
2. The ability to be qualitatively or quantitatively fit tested
in a reliable way to obtain a face-seal leakage of less than or
equal to 10% (54,55).
3. The ability to fit the different facial sizes and
characteristics of HCWs, which can usually be met by making the
respirators available in at least three sizes.
4. The ability to be checked for facepiece fit, in accordance
with standards established by the Occupational Safety and
Health Administration (OSHA) and good industrial hygiene
practice, by HCWs each time they put on their respirators
(54,55).
* The facility's risk assessment may identify a limited number
of selected settings (e.g., bronchoscopy performed on patients
suspected of having TB or autopsy performed on deceased persons
suspected of having had active TB at the time of death) where
the estimated risk for transmission of M. tuberculosis may be
such that a level of respiratory protection exceeding the
standard performance criteria is appropriate. In such
circumstances, a level of respiratory protection exceeding the
standard criteria and compatible with patient-care delivery
(e.g., more protective negative-pressure respirators; powered
air-purifying particulate respirators [PAPRs]; or
positive-pressure air-line, half-mask respirators) should be
provided by employers to HCWs who are exposed to M.
tuberculosis. Information on these and other respirators is in
the NIOSH Guide to Industrial Respiratory Protection (55) and
in Supplement 4 of this document.
* In some settings, HCWs may be at risk for two types of exposure:
a) inhalation of M. tuberculosis and b) mucous membrane
exposure to fluids that may contain bloodborne pathogens. In
these settings, protection against both types of exposure should
be used.
* When operative procedures (or other procedures requiring a
sterile field) are performed on patients who may have
infectious TB, respiratory protection worn by the HCW should
serve two functions: a) it should protect the surgical field
from the respiratory secretions of the HCW, and b) it should
protect the HCW from infectious droplet nuclei that may be
expelled by the patient or generated by the procedure.
Respirators with exhalation valves and most positive-pressure
respirators do not protect the sterile field.
* Health-care facilities in which respiratory protection is used
to prevent inhalation of M. tuberculosis are required by OSHA
to develop, implement, and maintain a respiratory protection
program (Suppl. 4). All HCWs who use respiratory protection
should be included in this program. Visitors to TB patients
should be given respirators to wear while in isolation rooms,
and they should be given general instructions on how to use
their respirators.
* Facilities that do not have isolation rooms and do not perform
cough-inducing procedures on patients who may have TB may not
need to have a respiratory protection program for TB. However,
such facilities should have written protocols for the early
identification of patients who have signs or symptoms of TB and
procedures for referring these patients to a facility where they
can be evaluated and managed appropriately. These protocols
should be evaluated regularly and revised as needed.
* Surgical masks are designed to prevent the respiratory secretions
of the person wearing the mask from entering the air. To reduce
the expulsion of droplet nuclei into the air, patients suspected
of having TB should wear surgical masks when not in TB isolation
rooms. These patients do not need to wear particulate
respirators, which are designed to filter the air before it is
inhaled by the person wearing the respirator. Patients suspected
of having or known to have TB should never wear a respirator that
has an exhalation valve, because this type of respirator does not
prevent expulsion of droplet nuclei into the air.
H. Cough-Inducing and Aerosol-Generating Procedures
1. General guidelines
Procedures that involve instrumentation of the lower
respiratory tract or induce coughing can increase the
likelihood of droplet nuclei being expelled into the air. These
cough-inducing procedures include endotracheal intubation and
suctioning, diagnostic sputum induction, aerosol treatments
(e.g., pentamidine therapy), and bronchoscopy. Other procedures
that can generate aerosols (e.g., irrigation of tuberculous
abscesses, homogenizing or lyophilizing tissue, or other
processing of tissue that may contain tubercle bacilli) are
also covered by these recommendations.
* Cough-inducing procedures should not be performed on
patients who may have infectious TB unless the procedures
are absolutely necessary and can be performed with
appropriate precautions.
* All cough-inducing procedures performed on patients who may
have infectious TB should be performed using local exhaust
ventilation devices (e.g., booths or special enclosures) or,
if this is not feasible, in a room that meets the
ventilation requirements for TB isolation.
* HCWs should wear respiratory protection when present in
rooms or enclosures in which cough-inducing procedures are
being performed on patients who may have infectious TB.
* After completion of cough-inducing procedures, patients who
may have infectious TB should remain in their isolation
rooms or enclosures and not return to common waiting areas
until coughing subsides. They should be given tissues and
instructed to cover their mouths and noses with the tissues
when coughing. If TB patients must recover from sedatives
or anesthesia after a procedure (e.g, after a bronchoscopy),
they should be placed in separate isolation rooms (and not
in recovery rooms with other patients) while they are being
monitored.
* Before the booth, enclosure, or room is used for another
patient, enough time should be allowed to pass for at
least 99% of airborne contaminants to be removed. This time
will vary according to the efficiency of the ventilation or
filtration used (Suppl. 3, Table S-31).
2. Special considerations for bronchoscopy
* If performing bronchoscopy in positive-pressure rooms
(e.g., operating rooms) is unavoidable, TB should be ruled
out as a diagnosis before the procedure is performed. If
the bronchoscopy is being performed for the purpose of
diagnosing pulmonary disease and that diagnosis could
include TB, the procedure should be performed in a room
that meets TB isolation ventilation requirements.
3. Special considerations for the administration of aerosolized
pentamidine
* Patients should be screened for active TB before prophylactic
therapy with aerosolized pentamidine is initiated. Screening
should include obtaining a medical history and performing
skin testing and chest radiography.
* Before each subsequent treatment with aerosolized
pentamidine, patients should be screened for symptoms
suggestive of TB (e.g., development of a productive cough).
If such symptoms are elicited, a diagnostic evaluation for
TB should be initiated.
* Patients who have suspected or confirmed active TB should
take, if clinically practical, oral prophylaxis for P.
carinii pneumonia.
I. Education and Training of HCWs
All HCWs, including physicians, should receive education regarding
TB that is relevant to persons in their particular occupational
group. Ideally, training should be conducted before initial
assignment, and the need for additional training should be
reevaluated periodically (e.g., once a year). The level and detail
of this education will vary according to the HCW's work
responsibilities and the level of risk in the facility (or area of
the facility) in which the HCW works. However, the program may
include the following elements:
* The basic concepts of M. tuberculosis transmission,
pathogenesis, and diagnosis, including information concerning
the difference between latent TB infection and active TB
disease, the signs and symptoms of TB, and the possibility of
reinfection.
* The potential for occupational exposure to persons who have
infectious TB in the health-care facility, including
information concerning the prevalence of TB in the community
and facility, the ability of the facility to properly isolate
patients who have active TB, and situations with increased risk
for exposure to M. tuberculosis.
* The principles and practices of infection control that reduce
the risk for transmission of M. tuberculosis, including
information concerning the hierarchy of TB infection-control
measures and the written policies and procedures of the
facility. Site-specific control measures should be provided to
HCWs working in areas that require control measures in addition
to those of the basic TB infection-control program.
* The purpose of PPD skin testing, the significance of a
positive PPD test result, and the importance of participating
in the skin-test program.
* The principles of preventive therapy for latent TB infection.
These principles include the indications, use, effectiveness,
and the potential adverse effects of the drugs (Suppl. 2).
* The HCW's responsibility to seek prompt medical evaluation if
a PPD test conversion occurs or if symptoms develop that could
be caused by TB. Medical evaluation will enable HCWs who have
TB to receive appropriate therapy and will help to prevent
transmission of M. tuberculosis to patients and other HCWs.
* The principles of drug therapy for active TB.
* The importance of notifying the facility if the HCW is
diagnosed with active TB so that contact investigation
procedures can be initiated.
* The responsibilities of the facility to maintain the
confidentiality of the HCW while ensuring that the HCW who has
TB receives appropriate therapy and is noninfectious before
returning to duty.
* The higher risks associated with TB infection in persons who
have HIV infection or other causes of severely impaired
cell-mediated immunity, including a) the more frequent and
rapid development of clinical TB after infection with M.
tuberculosis, b) the differences in the clinical presentation
of disease, and c) the high mortality rate associated with
MDR-TB in such persons.
* The potential development of cutaneous anergy as immune
function (as measured by CD4+ T-lymphocyte counts) declines.
* Information regarding the efficacy and safety of BCG
vaccination and the principles of PPD screening among BCG
recipients.
* The facility's policy on voluntary work reassignment options for
immunocompromised HCWs.
J. HCW Counseling, Screening, and Evaluation
* A TB counseling, screening, and prevention program for HCWs
should be established to protect both HCWs and patients. HCWs
who have positive PPD test results, PPD test conversions, or
symptoms suggestive of TB should be identified, evaluated to
rule out a diagnosis of active TB, and started on therapy or
preventive therapy if indicated (5). In addition, the results
of the HCW PPD screening program will contribute to evaluation
of the effectiveness of current infection-control practices.
1. Counseling HCWs regarding TB
* Because of the increased risk for rapid progression
from latent TB infection to active TB in HIV-infected or
otherwise severely immunocompromised persons, all HCWs
should know if they have a medical condition or are
receiving a medical treatment that may lead to severely
impaired cell-mediated immunity. HCWs who may be at risk
for HIV infection should know their HIV status (i.e.,
they should be encouraged to voluntarily seek counseling
and testing for HIV antibody status). Existing guidelines
for counseling and testing should be followed routinely
(56). Knowledge of these conditions allows the HCW to
seek the appropriate preventive measures outlined in this
document and to consider voluntary work reassignments. Of
particular importance is that HCWs need to know their HIV
status if they are at risk for HIV infection and they work
in settings where patients who have drug-resistant TB may
be encountered.
* All HCWs should be informed about the need to follow
existing recommendations for infection control to
minimize the risk for exposure to infectious agents;
implementation of these recommendations will greatly
reduce the risk for occupational infections among HCWs
(57). All HCWs should also be informed about the
potential risks to severely immunocompromised persons
associated with caring for patients who have some
infectious diseases, including TB. It should be
emphasized that limiting exposure to TB patients is the
most protective measure that severely immunosuppressed
HCWs can take to avoid becoming infected with M.
tuberculosis. HCWs who have severely impaired
cell-mediated immunity and who may be exposed to M.
tuberculosis may consider a change in job setting to
avoid such exposure. HCWs should be advised of the option
that severely immunocompromised HCWs can choose to
transfer voluntarily to areas and work activities in
which there is the lowest possible risk for exposure to
M. tuberculosis. This choice should be a personal
decision for HCWs after they have been informed of the
risks to their health.
* Employers should make reasonable accommodations (e.g.,
alternative job assignments) for employees who have a
health condition that compromises cell-mediated immunity
and who work in settings where they may be exposed to M.
tuberculosis. HCWs who are known to be immunocompromised
should be referred to employee health professionals who
can individually counsel the employees regarding their
risk for TB. Upon the request of the immunocompromised
HCW, employers should offer, but not compel, a work
setting in which the HCW would have the lowest possible
risk for occupational exposure to M. tuberculosis.
Evaluation of these situations should also include
consideration of the provisions of the Americans With
Disabilities Act of 1990* and other applicable federal,
state, and local laws.
__________
* Americans With Disabilities Act of 1990. PL 101-336, 42 U.S.C. 12101
et seq.
* All HCWs should be informed that immunosuppressed HCWs
should have appropriate follow-up and screening for
infectious diseases, including TB, provided by their
medical practitioner. HCWs who are known to be
HIV-infected or otherwise severely immunosuppressed
should be tested for cutaneous anergy at the time of PPD
testing (Suppl. 2). Consideration should be given to
retesting, at least every 6 months, those
immunocompromised HCWs who are potentially exposed to M.
tuberculosis because of the high risk for rapid
progression to active TB if they become infected.
* Information provided by HCWs regarding their immune
status should be treated confidentially. If the HCW
requests voluntary job reassignment, the confidentiality
of the HCW should be maintained. Facilities should have
written procedures on confidential handling of such
information.
2. Screening HCWs for active TB
* Any HCW who has a persistent cough (i.e., a cough
lasting greater than or equal to 3 weeks), especially in
the presence of other signs or symptoms compatible with
active TB (e.g., weight loss, night sweats, bloody sputum,
anorexia, or fever), should be evaluated promptly for TB.
The HCW should not return to the workplace until a
diagnosis of TB has been excluded or until the HCW is on
therapy and a determination has been made that the HCW
is noninfectious.
3. Screening HCWs for latent TB infection
* The risk assessment should identify which HCWs have
potential for exposure to M. tuberculosis and the
frequency with which the exposure may occur. This
information is used to determine which HCWs to include
in the skin-testing program and the frequency with which
they should be Table 2).
* If HCWs are from risks groups with increased prevalence
of TB, consideration may be given to including them in
the skin-testing program, even if they do not have
potential occupational exposure to M. tuberculosis, so
that converters can be identified and preventive therapy
offered.
* Administrators of health-care facilities should ensure
that physicians and other personnel not paid by, but
working in, the facility receive skin testing at
appropriate intervals for their occupational group and
work location.
* During the pre-employment physical or when applying for
hospital privileges, HCWs who have potential for exposure
to M. tuberculosis (Table 2), including those with a
history of BCG vaccination, should have baseline PPD skin
testing performed (Suppl. 2). For HCWs who have not had a
documented negative PPD test result during the preceding
12 months, the baseline PPD testing should employ the
two-step method; this will detect boosting phenomena that
might be misinterpreted as a skin-test conversion.
Decisions concerning the use of the two-step procedure
for baseline testing in a particular facility should be
based on the frequency of boosting in that facility.
* HCWs who have a documented history of a positive PPD
test, adequate treatment for disease, or adequate
preventive therapy for infection, should be exempt from
further PPD screening unless they develop signs or
symptoms suggestive of TB.
* PPD-negative HCWs should undergo repeat PPD testing at
regular intervals as determined by the risk assessment
(Section II.B). In addition, these HCWs should be tested
whenever they have been exposed to a TB patient and
appropriate precautions were not observed at the time of
exposure (Section II.K.3). Performing PPD testing of HCWs
who work in the same area or occupational group on
different scheduled dates (e.g., test them on their
birthdays or on their employment anniversary dates),
rather than testing all HCWs in the area or group on the
same day, may lead to earlier detection of M.
tuberculosis transmission.
* All PPD tests should be administered, read, and
interpreted in accordance with current guidelines by
specified trained personnel (Suppl. 2). At the time their
test results are read, HCWs should be informed about the
interpretation of both positive and negative PPD test
results. This information should indicate that the
interpretation of an induration that is 5-9 mm in
diameter depends on the HCW's immune status and history
of exposure to persons who have infectious TB.
Specifically, HCWs who have indurations of 5-9 mm in
diameter should be advised that such results may be
considered positive for HCWs who are contacts of persons
with infectious TB or who have HIV infection or other
causes of severe immunosuppression (e.g.,
immunosuppressive therapy for organ transplantation).
* When an HCW who is not assigned regularly to a single
work area has a PPD test conversion, appropriate personnel
should identify the areas where the HCW worked during the
time when infection was likely to have occurred. This
information can then be considered in analyzing the risk
for transmission in those areas.
* In any area of the facility where transmission of M.
tuberculosis is known to have occurred, a problem
evaluation should be conducted (Section II.K), and the
frequency of skin testing should be determined
according to the applicable risk category (Section II.B).
* PPD test results should be recorded confidentially in
the individual HCW's employee health record and in an
aggregate database of all HCW PPD test results. The
database can be analyzed periodically to estimate the
risk for acquiring new infection in specific areas or
occupational groups in the facility.
4. Evaluation and management of HCWs who have positive PPD
test results or active TB
a. Evaluation
* All HCWs with newly recognized positive PPD test
results or PPD test conversions should be evaluated
promptly for active TB. This evaluation should include
a clinical examination and a chest radiograph. If the
history, clinical examination, or chest radiograph is
compatible with active TB, additional tests should be
performed (Section II.C.2). If symptoms compatible
with TB are present, the HCW should be excluded from
the workplace until either a) a diagnosis of active TB
is ruled out or b) a diagnosis of active TB was
established, the HCW is being treated, and a
determination has been made that the HCW is
noninfectious (Suppl. 2). HCWs who do not have active
TB should be evaluated for preventive therapy
according to published guidelines (Suppl. 2).
* If an HCW's PPD test result converts to positive, a
history of confirmed or suspected TB exposure should
be obtained in an attempt to determine the potential
source. When the source of exposure is known, the
drug-susceptibility pattern of the M. tuberculosis
isolated from the source should be identified so that
the correct curative or preventive therapy can be
initiated for the HCW with the PPD test conversion.
The drug-susceptibility pattern should be recorded in
the HCW's medical record, where it will be available
if the HCW subsequently develops active TB and needs
therapy specific for the drug-susceptibility pattern.
* All HCWs, including those with histories of positive
PPD test results, should be reminded periodically
about the symptoms of TB and the need for prompt
evaluation of any pulmonary symptoms suggestive of TB.
b. Routine and follow-up chest radiographs
* Routine chest radiographs are not required for
asymptomatic, PPD-negative HCWs. HCWs with positive
PPD test results should have a chest radiograph as
part of the initial evaluation of their PPD test; if
negative, repeat chest radiographs are not needed
unless symptoms develop that could be attributed to
TB (58). However, more frequent monitoring for
symptoms of TB may be considered for recent converters
and other PPD-positive HCWs who are at increased risk
for developing active TB (e.g., HIV-infected or
otherwise severely immunocompromised HCWs).
c. Workplace restrictions
1) Active TB
* HCWs with pulmonary or laryngeal TB pose a risk to
patients and other HCWs while they are infectious,
and they should be excluded from the workplace until
they are noninfectious. The same work restrictions
apply to all HCWs regardless of their immune status.
* Before the HCW who has TB can return to the
work-place, the health-care facility should have
documentation from the HCW's health-care provider
that the HCW is receiving adequate therapy, the
cough has resolved, and the HCW has had three
consecutive negative sputum smears collected on
different days. After work duties are resumed
and while the HCW remains on anti-TB therapy,
facility staff should receive periodic
documentation from the HCW's health-care provider
that the HCW is being maintained on effective drug
therapy for the recommended time period and that
the sputum AFB smears continue to be negative.
* HCWs with active laryngeal or pulmonary TB who
discontinue treatment before they are cured should
be evaluated promptly for infectiousness. If the
evaluation determines that they are still
infectious, they should be excluded from the
workplace until treatment has been resumed, an
adequate response to therapy has been documented,
and three more consecutive sputum AFB smears
collected on different days have been negative.
* HCWs who have TB at sites other than the lung or
larynx usually do not need to be excluded from the
workplace if a diagnosis of concurrent pulmonary
TB has been ruled out.
2) Latent TB infection
* HCWs receiving preventive treatment for latent TB
infection should not be restricted from their
usual work activities.
* HCWs with latent TB infection who cannot take or
who do not accept or complete a full course of
preventive therapy should not be excluded from the
work-place. These HCWs should be counseled about
the risk for developing active TB and instructed
regularly to seek prompt evaluation if signs or
symptoms develop that could be caused by TB.
K. Problem Evaluation
Epidemiologic investigations may be indicated for several
situations. These include, but are not limited to, a) the
occurrence of PPD test conversions or active TB in HCWs; b) the
occurrence of possible person-to-person transmission of M.
tuberculosis; and c) situations in which patients or HCWs with
active TB are not promptly identified and isolated, thus exposing
other persons in the facility to M. tuberculosis. The general
objectives of the epidemiologic investigations in these
situations are as follows:
1) to determine the likelihood that transmission of and
infection with M. tuberculosis has occurred in the facility;
2) to determine the extent to which M. tuberculosis has been
transmitted;
3) to identify those persons who have been exposed and infected,
enabling them to receive appropriate clinical management;
4) to identify factors that could have contributed to
transmission and infection and to implement appropriate
interventions; and
5) to evaluate the effectiveness of any interventions that are
implemented and to ensure that exposure to and transmission of
M. tuberculosis have been terminated.
The exact circumstances of these situations are likely to vary
considerably, and the associated epidemiologic investigations
should be tailored to the individual circumstances. The following
sections provide general guidance for conducting these
investigations.
1. Investigating PPD test conversions and active TB in HCWs
a. Investigating PPD test conversions in HCWs
PPD test conversions may be detected in HCWs as a result of
a contact investigation, in which case the probable source
of exposure and transmission is already known (Section
II.K.3.), or as a result of routine screening, in which case
the probable source of exposure and infection is not already
known and may not be immediately apparent.
If a skin-test conversion in an HCW is identified as part
of routine screening, the following steps should be
considered (Figure 2):
* The HCW should be evaluated promptly for active TB.
The initial evaluation should include a thorough history,
physical examination, and chest radiograph. On the basis
of the initial evaluation, other diagnostic procedures
(e.g., sputum examination) may be indicated.
* If appropriate, the HCW should be placed on preventive
or curative therapy in accordance with current
guidelines (Suppl. 2) (5).
* A history of possible exposure to M. tuberculosis should
be obtained from the HCW to determine the most likely
source of infection. When the source of infection is
known, the drug-susceptibility pattern of the M.
tuberculosis isolate from the source patient should be
identified to determine appropriate preventive or
curative therapy regimens.
* If the history suggests that the HCW was exposed to and
infected with M. tuberculosis outside the facility, no
further epidemiologic investigation to identify a source
in the facility is necessary.
* If the history does not suggest that the HCW was exposed
and infected outside the facility but does identify a
probable source of exposure in the facility, contacts of
the suspected source patient should be identified and
evaluated. Possible reasons for the exposure and
transmission should be evaluated (Table 4), interventions
should be implemented to correct these causes, and PPD
testing of PPD-negative HCWs should be performed
immediately and repeated after 3 months.
If no additional PPD test conversions are detected on
follow-up testing, the investigation can be terminated.
If additional PPD test conversions are detected on
follow-up testing, the possible reasons for exposure and
transmission should be reassessed, the appropriateness
of and degree of adherence to the interventions
implemented should be evaluated, and PPD testing of
PPD-negative HCWs should be repeated after another 3
months.
If no additional PPD test conversions are detected on the
second round of follow-up testing, the investigation can
be terminated. However, if additional PPD conversions are
detected on the second round of follow-up testing, a
high-risk protocol should be implemented in the affected
area or occupational group, and the public health
department or other persons with expertise in TB
infection control should be consulted.
* If the history does not suggest that the HCW was exposed
to and infected with M. tuberculosis outside the facility
and does not identify a probable source of exposure in
the facility, further investigation to identify the
probable source patient in the facility is warranted.
The interval during which the HCW could have been
infected should be estimated. Generally, this would be
the interval from 10 weeks before the most recent
negative PPD test through 2 weeks before the first
positive PPD test (i.e., the conversion).
Laboratory and infection-control records should be
reviewed to identify all patients or HCWs who have
suspected or confirmed infectious TB and who could have
transmitted M. tuberculosis to the HCW.
If this process does identify a likely source patient,
contacts of the suspected source patient should be
identified and evaluated, and possible reasons for the
exposure and transmission should be evaluated (Table 4).
Interventions should be implemented to correct these
causes, and PPD testing of PPD-negative HCWs should be
repeated after 3 months. However, if this process does
not identify a probable source case, PPD screening
results of other HCWs in the same area or occupational
group should be reviewed for additional evidence of M.
tuberculosis transmission. If sufficient additional PPD
screening results are not available, appropriate
personnel should consider conducting additional PPD
screening of other HCWs in the same area or occupational
group.
(For Figure 2, see printed copy)
(For Table 4, see printed copy)
If this review and/or screening does not identify
additional PPD conversions, nosocomial transmission is
less likely, and the contact investigation can probably
be terminated. Whether the HCW's PPD test conversion
resulted from occupational exposure and infection is
uncertain; however, the absence of other data
implicating nosocomial transmission suggests that the
conversion could have resulted from a) unrecognized
exposure to M. tuberculosis outside the facility; b)
cross-reactivity with another antigen (e.g.,
nontuberculous mycobacteria); c) errors in applying,
reading, or interpreting the test; d) false positivity
caused by the normal variability of the test; or e)
false positivity caused by a defective PPD preparation.
If this review and/or screening does identify additional
PPD test conversions, nosocomial transmission is more
likely. In this situation, the patient identification
(i.e., triage) process, TB infection-control policies and
practices, and engineering controls should be evaluated
to identify problems that could have led to exposure
and transmission (Table 4).
If no such problems are identified, a high-risk protocol
should be implemented in the affected area or
occupational group, and the public health department or
other persons with expertise in TB infection control
should be consulted.
If such problems are identified, appropriate
interventions should be implemented to correct the
problem(s), and PPD skin testing of PPD-negative HCWs
should be repeated after 3 months.
If no additional PPD conversions are detected on
follow-up testing, the investigation can be terminated.
If additional PPD conversions are detected on follow-up
testing, the possible reasons for exposure and
transmission should be reassessed, the appropriateness
of and adherence to the interventions implemented should
be evaluated, and PPD skin testing of PPD-negative HCWs
should be repeated after another 3 months.
If no additional PPD test conversions are detected on
this second round of follow-up testing, the
investigation can be terminated. However, if additional
PPD test conversions are detected on the second round
of follow-up testing, a high-risk protocol should be
implemented in the affected area or occupational group,
and the public health department or other persons with
expertise in TB infection control should be consulted.
b. Investigating cases of active TB in HCWs
If an HCW develops active TB, the following steps should
be taken:
* The case should be evaluated epidemiologically, in a
manner similar to PPD test conversions in HCWs, to
determine the likelihood that it resulted from
occupational transmission and to identify possible causes
and implement appropriate interventions if the evaluation
suggests such transmission.
* Contacts of the HCW (e.g., other HCWs, patients,
visitors, and others who have had intense exposure to
the HCW) should be identified and evaluated for TB
infection and disease (Section II.K.3; Suppl. 2). The
public health department should be notified immediately
for consultation and to allow for investigation of
community contacts who were not exposed in the
health-care facility.
* The public health department should notify facilities
when HCWs with TB are reported by physicians so that an
investigation of contacts can be conducted in the
facility. The information provided by the health
department to facilities should be in accordance with
state or local laws to protect the confidentiality of
the HCW.
2. Investigating possible patient-to-patient transmission of M.
tuberculosis
Surveillance of active TB cases in patients should be conducted.
If this surveillance suggests the possibility of
patient-to-patient transmission of M. tuberculosis (e.g., a
high proportion of TB patients had prior admissions during the
year preceding onset of their TB, the number of patients with
drug-resistant TB increased suddenly, or isolates obtained from
multiple patients had identical and characteristic
drug-susceptibility or DNA fingerprint patterns), the
following steps should be taken:
* Review the HCW PPD test results and patient surveillance data
for the suspected areas to detect additional patients or HCWs
with PPD test conversions or active disease.
* Look for possible exposures that patients with newly
diagnosed TB could have had to other TB patients during
previous admissions. For example, were the patients
admitted to the same room or area, or did they receive the
same procedure or go to the same treatment area on the same
day?
If the evaluation thus far suggests transmission has occurred,
the following steps should be taken:
* Evaluate possible causes of the transmission (e.g., problem
with patient detection, institutional barriers to
implementing appropriate isolation practices, or inadequate
engineering controls) (Table 4).
* Ascertain whether other patients or HCWs could have been
exposed; if so, evaluate these persons for TB infection and
disease (Section II.K.3; Suppl. 2).
* Notify the public health department so they can begin a
community contact investigation if necessary.
3. Investigating contacts of patients and HCWs who have infectious
TB
If a patient who has active TB is examined in a health-care
facility and the illness is not diagnosed correctly, resulting
in failure to apply appropriate precautions, or if an HCW
develops active TB and exposes other persons in the facility,
the following steps should be taken when the illness is later
diagnosed correctly:
* To identify other patients and HCWs who were exposed to
the source patient before isolation procedures were begun,
interview the source patient and all applicable personnel
and review that patient's medical record. Determine the
areas of the facility in which the source patient was
hospitalized, visited, or worked before being placed in
isolation (e.g., outpatient clinics, hospital rooms,
treatment rooms, radiology and procedure areas, and patient
lounges) and the HCWs who may have been exposed during that
time (e.g., persons providing direct care, therapists,
clerks, transportation personnel, housekeepers, and social
workers).
* The contact investigation should first determine if M.
tuberculosis transmission has occurred from the source
patient to those persons with whom the source patient had
the most intense contact.
* Administer PPD tests to the most intensely exposed HCWs and
patients as soon as possible after the exposure has occurred.
If transmission did occur to the most intensely exposed
persons, then those persons with whom the patient had less
contact should be evaluated. If the initial PPD test result
is negative, a second test should be administered 12 weeks
after the exposure was terminated.
* Those persons who were exposed to M. tuberculosis and who
have either a PPD test conversion or symptoms suggestive of
TB should receive prompt clinical evaluation and, if
indicated, chest radiographs and bacteriologic studies should
be performed (Suppl. 2). Those persons who have evidence of
newly acquired infection or active disease should be
evaluated for preventive or curative therapy (Suppl. 2).
Persons who have previously had positive PPD test results
and who have been exposed to an infectious TB patient do
not require a repeat PPD test or a chest radiograph unless
they have symptoms suggestive of TB.
* In addition to PPD testing those HCWs and patients who have
been exposed to M. tuberculosis because a patient was not
isolated promptly or an HCW with active TB was not
identified promptly, the investigation should determine why
the diagnosis of TB was delayed. If the correct diagnosis
was made but the patient was not isolated promptly, the
reasons for the delay need to be defined so that corrective
actions can be taken.
L. Coordination with the Public Health Department
* As soon as a patient or HCW is known or suspected to have active
TB, the patient or HCW should be reported to the public health
department so that appropriate follow-up can be arranged and a
community contact investigation can be performed. The health
department should be notified well before patient discharge to
facilitate follow-up and continuation of therapy. A discharge
plan coordinated with the patient or HCW, the health department,
and the inpatient facility should be implemented.
* The public health department should protect the confidentiality
of the patient or HCW in accordance with state and local laws.
* Health-care facilities and health departments should coordinate
their efforts to perform appropriate contact investigations on
patients and HCWs who have active TB.
* In accordance with state and local laws and regulations,
results of all AFB-positive sputum smears, cultures positive
for M. tuberculosis, and drug-susceptibility results on M.
tuberculosis isolates should be reported to the public health
department as soon as these results are available.
* The public health department may be able to assist facilities
with planning and implementing various aspects of a TB
infection-control program (e.g., surveillance, screening
activities, and outbreak investigations). In addition, the state
health department may be able to provide names of experts to
assist with the engineering aspects of TB infection control.
M. Additional Considerations for Selected Areas in Health-Care
Facilities and Other Health-Care Settings
This section contains additional information for selected areas in
health-care facilities and for other health-care settings.
1. Selected areas in health-care facilities
a. Operating rooms
* Elective operative procedures on patients who have TB
should be delayed until the patient is no longer
infectious.
* If operative procedures must be performed, they should
be done, if possible, in operating rooms that have
anterooms. For operating rooms without anterooms, the
doors to the operating room should be closed, and
traffic into and out of the room should be minimal to
reduce the frequency of opening and closing the door.
Attempts should be made to perform the procedure at a
time when other patients are not present in the operative
suite and when a minimum number of personnel are present
(e.g., at the end of day).
* Placing a bacterial filter on the patient endotracheal
tube (or at the expiratory side of the breathing
circuit of a ventilator or anesthesia machine if these
are used) when operating on a patient who has confirmed
or suspected TB may help reduce the risk for contaminating
anesthesia equipment or discharging tubercle bacilli into
the ambient air.
* During postoperative recovery, the patient should be
monitored and should be placed in a private room that
meets recommended standards for ventilating TB isolation
rooms.
* When operative procedures (or other procedures requiring
a sterile field) are performed on patients who may have
infectious TB, respiratory protection worn by the HCW
must protect the field from the respiratory secretions
of the HCW and protect the HCW from the infectious
droplet nuclei generated by the patient. Valved or
positive-pressure respirators do not protect the sterile
field; therefore, a respirator that does not have a
valve and that meets the criteria in Section II.G should
be used.
b. Autopsy rooms
* Because infectious aerosols are likely to be present in
autopsy rooms, such areas should be at negative pressure
with respect to adjacent areas (Suppl. 3), and the room
air should be exhausted directly to the outside of the
building. ASHRAE recommends that autopsy rooms have
ventilation that provides an airflow of 12 ACH (47),
although the effectiveness of this ventilation level in
reducing the risk for M. tuberculosis transmission has
not been evaluated. Where possible, this level should be
increased by means of ventilation system design or by
auxiliary methods (e.g., recirculation of air within the
room through HEPA filters) (Suppl. 3).
* Respiratory protection should be worn by personnel while
performing autopsies on deceased persons who may have
had TB at the time of death (Section II.G; Suppl. 4).
* Recirculation of HEPA-filtered air within the room or
UVGI may be used as a supplement to the recommended
ventilation (Suppl. 3).
c. Laboratories
* Laboratories in which specimens for mycobacteriologic
studies (e.g., AFB smears and cultures) are processed
should be designed to conform with criteria specified by
CDC and the National Institutes of Health (59).
2. Other health-care settings
TB precautions may be appropriate in a number of other types of
health-care settings. The specific precautions that are applied
will vary depending on the setting. At a minimum, a risk
assessment should be performed yearly for these settings; a
written TB infection-control plan should be developed, evaluated,
and revised on a regular basis; protocols should be in place for
identifying and managing patients who may have active TB; HCWs
should receive appropriate training, education, and screening;
protocols for problem evaluation should be in place; and
coordination with the public health department should be
arranged when necessary. Other recommendations specific to
certain of these settings follow.
a. Emergency medical services
* When EMS personnel or others must transport patients who
have confirmed or suspected active TB, a surgical mask
should be placed, if possible, over the patient's mouth
and nose. Because administrative and engineering controls
during emergency transport situations cannot be ensured,
EMS personnel should wear respiratory protection when
transporting such patients. If feasible, the windows of
the vehicle should be kept open. The heating and
air-conditioning system should be set on a
nonrecirculating cycle.
* EMS personnel should be included in a comprehensive PPD
screening program and should receive a baseline PPD test
and follow-up testing as indicated by the risk
assessment. They should also be included in the
follow-up of contacts of a patient with infectious TB.*
__________
* The Ryan White Comprehensive AIDS Resource Emergency Act of 1990,
P.L. 101-381, mandates notification of EMS personnel after they have been
exposed to infectious pulmonary TB (42 U.S.C. 300ff-82.54 Fed. Reg. 13417
[March 21, 1994]).
b. Hospices
* Hospice patients who have confirmed or suspected TB
should be managed in the manner described in this
document for management of TB patients in hospitals.
General-use and specialized areas (e.g., treatment or
TB isolation rooms) should be ventilated in the same
manner as described for similar hospital areas.
c. Long-term care facilities
* Recommendations published previously for preventing and
controlling TB in long-term care facilities should be
followed (60).
* Long-term care facilities should also follow the
recommendations outlined in this document.
d. Correctional facilities
* Recommendations published previously for preventing and
controlling TB in correctional facilities should be
followed (61).
* Prison medical facilities should also follow the
recommendations outlined in this document.
e. Dental settings
In general, the symptoms for which patients seek treatment
in a dental-care setting are not likely to be caused by
infectious TB. Unless a patient requiring dental care
coincidentally has TB, it is unlikely that infectious TB
will be encountered in the dental setting. Furthermore,
generation of droplet nuclei containing M. tuberculosis
during dental procedures has not been demonstrated (62).
Therefore, the risk for transmission of M. tuberculosis in
most dental settings is probably quite low. Nevertheless,
during dental procedures, patients and dental workers share
the same air for varying periods of time. Coughing may be
stimulated occasionally by oral manipulations, although no
specific dental procedures have been classified as
"cough-inducing." In some instances, the population served
by a dental-care facility, or the HCWs in the facility, may
be at relatively high risk for TB. Because the potential
exists for transmission of M. tuberculosis in dental
settings, the following recommendations should be followed:
* A risk assessment (Section II.B) should be done
periodically, and TB infection-control policies for each
dental setting should be based on the risk assessment.
The policies should include provisions for detection and
referral of patients who may have undiagnosed active TB;
management of patients with active TB, relative to
provision of urgent dental care; and employer-sponsored
HCW education, counseling, and screening.
* While taking patients' initial medical histories and at
periodic updates, dental HCWs should routinely ask all
patients whether they have a history of TB disease and
symptoms suggestive of TB.
* Patients with a medical history or symptoms suggestive of
undiagnosed active TB should be referred promptly for
medical evaluation of possible infectiousness. Such
patients should not remain in the dental-care facility
any longer than required to arrange a referral. While in
the dental-care facility, they should wear surgical masks
and should be instructed to cover their mouths and noses
when coughing or sneezing.
* Elective dental treatment should be deferred until a
physician confirms that the patient does not have
infectious TB. If the patient is diagnosed as having
active TB, elective dental treatment should be deferred
until the patient is no longer infectious.
* If urgent dental care must be provided for a patient who
has, or is strongly suspected of having, infectious TB,
such care should be provided in facilities that can
provide TB isolation (Sections II.E and G). Dental HCWs
should use respiratory protection while performing
procedures on such patients.
* Any dental HCW who has a persistent cough (i.e., a cough
lasting greater than or equal to 3 weeks), especially in
the presence of other signs or symptoms compatible with
active TB (e.g., weight loss, night sweats, bloody sputum,
anorexia, and fever), should be evaluated promptly for TB.
The HCW should not return to the work-place until a
diagnosis of TB has been excluded or until the HCW is on
therapy and a determination has been made that the HCW
is noninfectious.
* In dental-care facilities that provide care to
populations at high risk for active TB, it may be
appropriate to use engineering controls similar to those
used in general-use areas (e.g., waiting rooms) of
medical facilities that have a similar risk profile.
f. Home-health-care settings
* HCWs who provide medical services in the homes of
patients who have suspected or confirmed infectious TB
should instruct such patients to cover their mouths and
noses with a tissue when coughing or sneezing. Until
such patients are no longer infectious, HCWs should wear
respiratory protection when entering these patients'
homes (Suppl. 4).
* Precautions in the home may be discontinued when the
patient is no longer infectious (Suppl. 1).
* HCWs who provide health-care services in their patients'
homes can assist in preventing transmission of M.
tuberculosis by educating their patients regarding the
importance of taking medications as prescribed and by
administering DOT.
* Cough-inducing procedures performed on patients who have
infectious TB should not be done in the patients' homes
unless absolutely necessary. When medically necessary
cough-inducing procedures (e.g., AFB sputum collection for
evaluation of therapy) must be performed on patients who
may have infectious TB, the procedures should be performed
in a health-care facility in a room or booth that has the
recommended ventilation for such procedures. If these
procedures must be performed in a patient's home, they
should be performed in a well-ventilated area away from
other household members. If feasible, the HCW should
consider opening a window to improve ventilation or
collecting the specimen while outside the dwelling. The
HCW collecting these specimens should wear respiratory
protection during the procedure (Section II.G).
* HCWs who provide medical services in their patients'
homes should be included in comprehensive
employer-sponsored TB training, education, counseling,
and screening programs. These programs should include
provisions for identifying HCWs who have active TB,
baseline PPD skin testing, and follow-up PPD testing at
intervals appropriate to the degree of risk.
* Patients who are at risk for developing active TB and
the HCWs who provide medical services in the homes of
such patients should be reminded periodically of the
importance of having pulmonary symptoms evaluated
promptly to permit early detection of and treatment for
TB.
g. Medical offices
In general, the symptoms of active TB are symptoms for which
patients are likely to seek treatment in a medical office.
Furthermore, the populations served by some medical offices,
or the HCWs in the office, may be at relatively high risk
for TB. Thus, it is likely that infectious TB will be
encountered in a medical office. Because of the potential
for M. tuberculosis transmission, the following
recommendations should be observed:
* A risk assessment should be conducted periodically, and
TB infection-control policies based on results of the
risk assessment should be developed for the medical
office. The policies should include provisions for
identifying and managing patients who may have undiagnosed
active TB; managing patients who have active TB; and
educating, training, counseling, and screening HCWs.
* While taking patients' initial medical histories and at
periodic updates, HCWs who work in medical offices should
routinely ask all patients whether they have a history of
TB disease or have had symptoms suggestive of TB.
* Patients with a medical history and symptoms suggestive
of active TB should receive an appropriate diagnostic
evaluation for TB and be evaluated promptly for possible
infectiousness. Ideally, this evaluation should be done
in a facility that has TB isolation capability. At a
minimum, the patient should be provided with and asked to
wear a surgical mask, instructed to cover the mouth and
nose with a tissue when coughing or sneezing, and
separated as much as possible from other patients.
* Medical offices that provide evaluation or treatment
services for TB patients should follow the
recommendations for managing patients in ambulatory-care
settings (Section II.D).
* If cough-inducing procedures are to be administered in a
medical office to patients who may have active TB,
appropriate precautions should be followed (Section II.H).
* Any HCW who has a persistent cough (i.e., a cough lasting
greater than or equal to 3 weeks), especially in the
presence of other signs or symptoms compatible with
active TB (e.g., weight loss, night sweats, bloody
sputum, anorexia, or fever) should be evaluated promptly
for TB. HCWs with such signs or symptoms should not
return to the workplace until a diagnosis of TB has been
excluded or until they are on therapy and a
determination has been made that they are noninfectious.
* HCWs who work in medical offices in which there is a
likelihood of exposure to patients who have infectious
TB should be included in employer-sponsored education,
training, counseling, and PPD testing programs
appropriate to the level of risk in the office.
* In medical offices that provide care to populations at
relatively high risk for active TB, use of engineering
controls as described in this document for general-use
areas (e.g., waiting rooms) may be appropriate (Section
II.F; Suppl. 3).
Supplement 1: Determining the Infectiousness of a TB Patient
The infectiousness of patients with TB correlates with the number of
organisms expelled into the air, which, in turn, correlates with the
following factors: a) disease in the lungs, airways, or larynx; b)
presence of cough or other forceful expiratory measures; c) presence of
acid-fast bacilli (AFB) in the sputum; d) failure of the patient to cover
the mouth and nose when coughing; e) presence of cavitation on chest
radiograph; f) inappropriate or short duration of chemotherapy; and g)
administration of procedures that can induce coughing or cause
aerosolization of M. tuberculosis (e.g., sputum induction).
The most infectious persons are most likely those who have not been
treated for TB and who have either a) pulmonary or laryngeal TB and a
cough or are undergoing cough-inducing procedures, b) a positive AFB
sputum smear, or c) cavitation on chest radiograph. Persons with
extrapulmonary TB usually are not infectious unless they have a)
concomitant pulmonary disease; b) nonpulmonary disease located in the
respiratory tract or oral cavity; or c) extrapulmonary disease that
includes an open abscess or lesion in which the concentration of organisms
is high, especially if drainage from the abscess or lesion is extensive
(20,22). Coinfection with HIV does not appear to affect the
infectiousness of TB patients (63-65).
In general, children who have TB may be less likely than adults to be
infectious; however, transmission from children can occur. Therefore,
children with TB should be evaluated for infectiousness using the same
parameters as for adults (i.e., pulmonary or laryngeal TB, presence of
cough or cough-inducing procedures, positive sputum AFB smear, cavitation
on chest radiograph, and adequacy and duration of therapy). Pediatric
patients who may be infectious include those who a) are not on therapy, b)
have just been started on therapy, or c) are on inadequate therapy, and
who a) have laryngeal or extensive pulmonary involvement, b) have
pronounced cough or are undergoing cough-inducing procedures, c) have
positive sputum AFB smears, or d) have cavitary TB. Children who have
typical primary tuberculous lesions and do not have any of the indicators
of infectiousness listed previously usually do not need to be placed in
isolation. Because the source case for pediatric TB patients often occurs
in a member of the infected child's family (45), parents and other
visitors of all pediatric TB patients should be evaluated for TB as soon
as possible.
Infection is most likely to result from exposure to persons who have
unsuspected pulmonary TB and are not receiving anti-TB therapy or from
persons who have diagnosed TB and are not receiving adequate therapy.
Administration of effective anti-TB therapy has been associated with
decreased infectiousness among persons who have active TB (66). Effective
therapy reduces coughing, the amount of sputum produced, and the number of
organisms in the sputum. However, the period of time a patient must take
effective therapy before becoming noninfectious varies between patients
(67). For example, some TB patients are never infectious, whereas those
with unrecognized or inadequately treated drug-resistant TB may remain
infectious for weeks or months (24). Thus, decisions about infectiousness
should be made on an individual basis.
In general, patients who have suspected or confirmed active TB should be
considered infectious if they a) are coughing, b) are undergoing
cough-inducing procedures, or c) have positive AFB sputum smears, and if
they a) are not on chemotherapy, b) have just started chemotherapy, or c)
have a poor clinical or bacteriologic response to chemotherapy. A patient
who has drug-susceptible TB and who is on adequate chemotherapy and has
had a significant clinical and bacteriologic response to therapy (i.e.,
reduction in cough, resolution of fever, and progressively decreasing
quantity of bacilli on smear) is probably no longer infectious. However,
because drug-susceptibility results are not usually known when the
decision to discontinue isolation is made, all TB patients should remain
in isolation while hospitalized until they have had three consecutive
negative sputum smears collected on different days and they demonstrate
clinical improvement.
Supplement 2: Diagnosis and Treatment of Latent TB Infection and Active TB
I. Diagnostic Procedures for TB Infection and Disease
A diagnosis of TB may be considered for any patient who has a
persistent cough (i.e., a cough lasting greater than or equal to 3
weeks) or other signs or symptoms compatible with TB (e.g., bloody
sputum, night sweats, weight loss, anorexia, or fever). However, the
index of suspicion for TB will vary in different geographic areas and
will depend on the prevalence of TB and other characteristics of the
population served by the facility. The index of suspicion for TB
should be very high in areas or among groups of patients in which the
prevalence of TB is high (Section I.B). Persons for whom a diagnosis
of TB is being considered should receive appropriate diagnostic tests,
which may include PPD skin testing, chest radiography, and
bacteriologic studies (e.g., sputum microscopy and culture).
A. PPD Skin Testing and Anergy Testing
1. Application and reading of PPD skin tests
The PPD skin test is the only method available for demonstrating
infection with M. tuberculosis. Although currently available
PPD tests are less than 100% sensitive and specific for
detection of infection with M. tuberculosis, no better
diagnostic methods have yet been devised. Interpretation of
PPD test results requires knowledge of the antigen used, the
immunologic basis for the reaction to this antigen, the
technique used to administer and read the test, and the
results of epidemiologic and clinical experience with the test
(2,5,6). The PPD test, like all medical tests, is subject to
variability, but many of the variations in administering and
reading PPD tests can be avoided by proper training and
careful attention to details.
The intracutaneous (Mantoux) administration of a measured amount
of PPD-tuberculin is currently the preferred method for doing
the test. One-tenth milliliter of PPD (5 TU) is injected just
beneath the surface of the skin on either the volar or dorsal
surface of the forearm. A discrete, pale elevation of the skin
(i.e., a wheal) that is 6-10 mm in diameter should be produced.
PPD test results should be read by designated, trained personnel
between 48 and 72 hours after injection. Patient or HCW
self-reading of PPD test results should not be accepted (68).
The result of the test is based on the presence or absence of an
induration at the injection site. Redness or erythema should
not be measured. The transverse diameter of induration should
be recorded in millimeters.
2. Interpretation of PPD skin tests
a. General
The interpretation of a PPD reaction should be influenced
by the purpose for which the test was given (e.g.,
epidemiologic versus diagnostic purposes), by the prevalence
of TB infection in the population being tested, and by the
consequences of false classification. Errors in
classification can be minimized by establishing an
appropriate definition of a positive reaction (Table S2-1").
The positive-predictive value of PPD tests (i.e, the
probability that a person with a positive PPD test is
actually infected with M. tuberculosis) is dependent on the
prevalence of TB infection in the population being tested
and the specificity of the test (69,70). In populations with
a low prevalence of TB infection, the probability that a
positive PPD test represents true infection with M.
tuberculosis is very low if the cut-point is set too low
(i.e., the test is not adequately specific). In populations
with a high prevalence of TB infection, the probability that
a positive PPD test using the same cut-point represents true
infection with M. tuberculosis is much higher. To ensure
that few persons infected with tubercle bacilli will be
misclassified as having negative reactions and few persons
not infected with tubercle bacilli will be misclassified as
having positive reactions, different cut-points are used to
separate positive reactions from negative reactions for
different populations, depending on the risk for TB
infection in that population.
A lower cut-point (i.e., 5 mm) is used for persons in the
highest risk groups, which include HIV-infected persons,
recent close contacts of persons with TB (e.g., in the
household or in an unprotected occupational exposure
similar in intensity and duration to household contact),
and persons who have abnormal chest radiographs with
fibrotic changes consistent with inactive TB. A higher
cut-point (i.e., 10 mm) is used for persons who are not in
the highest risk group but who have other risk factors
(e.g., injecting-drug users known to be HIV seronegative;
persons with certain medical conditions that increase the
risk for progression from latent TB infection to active TB
[Table S2-1]); medically under-served, low-income
populations; persons born in foreign countries that have a
high prevalence of TB; and residents of correctional
institutions and nursing homes). An even higher cut-point
(i.e., 15 mm) is used for all other persons who have none
of the above risk factors.
Recent PPD converters are considered members of a high-risk
group. A greater than or equal to 10 mm increase in the size
of the induration within a 2-year period is classified as a
conversion from a negative to a positive test result for
persons less than 35 years of age. An increase of induration
of greater than or equal to 15 mm within a 2-year period is
classified as a conversion for persons greater than or equal
to 35 years of age (5).
b. HCWs
In general, HCWs should have their skin-test results
interpreted according to the recommendations in this
supplement and in sections 1, 2, 3, and 5 of Table S2-1.
However, the prevalence of TB in the facility should be
considered when choosing the appropriate cut-point for
defining a positive PPD reaction. In facilities where there
is essentially no risk for exposure to TB patients (i.e.,
minimal- or very low-risk facilities [Section II.B]), an
induration greater than or equal to 15 mm may be an
appropriate cut-point for HCWs who have no other risk
factors. In other facilities where TB patients receive
care, the appropriate cut-point for HCWs who have no other
risk factors may be greater than or equal to 10 mm.
A recent PPD test conversion in an HCW should be defined
generally as an increase of greater than or equal to 10 mm
in the size of induration within a 2-year period. For HCWs
in facilities where exposure to TB is very unlikely (e.g.,
minimal-risk facilities), an increase of greater than or
equal to 15 mm within a 2-year period may be more
appropriate for defining a recent conversion because of the
lower positive-predictive value of the test in such groups.
3. Anergy testing
HIV-infected persons may have suppressed reactions to PPD
skin tests because of anergy, particularly if their CD4+
T-lymphocyte counts decline (71). Persons with anergy will
have a negative PPD test regardless of infection with M.
tuberculosis. HIV-infected testing (72). Two companion
antigens (e.g., Candida antigen and tetanus toxoid) should
be administered in addition to PPD. Persons with greater
than or equal to 3 mm of induration to any of the skin
tests (including tuberculin) are considered not anergic.
Reactions of greater than or equal to 5 mm to PPD are
considered to be evidence of TB infection in HIV-infected
persons regardless of the reactions to the companion
antigens. If there is no reaction (i.e., less than 3 mm
induration) to any of the antigens, the person being tested
is considered anergic. Determination of whether such
persons are likely to be infected with M. tuberculosis must
be based on other epidemiologic factors (e.g., the
proportion of other persons with the same level of exposure
who have positive PPD test results and the intensity or
duration of exposure to infectious TB patients that the
anergic person experienced).
4. Pregnancy and PPD skin testing
Although thousands (perhaps millions) of pregnant women
have been PPD skin tested since the test was devised, thus
far no documented episodes of fetal harm have resulted from
use of the tuberculin test (73). Pregnancy should not
exclude a female HCW from being skin tested as part of a
contact investigation or as part of a regular skin-testing
program.
TABLE S2-1. Summary of interpretation of purified protein derivation
(PPD-tubercilin skin-test results
-----------------------------------------------------------------------------
1. An induration of greater than or equals to 5 mm is classified as
positive in:
* persons who have human immunodeficiency virus (HIV) infection or
risk factors for HIV infection but unknown HIV status;
* persons who have had recent close contact* with persons who have
active tuberculosis (TB);
* Recent close contact inplies either househould or social contact or
unprotected occupational exposure similar in intensity and duration to
househould contact.
* persons who have fibrotic chest radiographs (consistent with healed
TB).
2. An induration of greater than or equals to 10 mm is classified as
positive in all persons who do not meet any of the criteria above but
who have other risk factors for TB, including:
High-risk groups--
* injection-drug users known to be HIV seronegative;
* persons who have other medical conditions that reportedly increase
the risk for progressing from latent TB infection to active TB
(e.g., silicosis; gastrectomy or jejuno-ioeal bypass; being greater
than or equal to 10% below ideal body weight; chronic renal failure
with renal dialysis; diabetes mellitus; high-dose corticosteroid or
other immunosuppressive therapy; some hematologic disorders,
including malignancies such as leukemias and lymphomas; and other
malignancies);
* children less than or equal to 4 years of age.
High-prevalence groups--
* persons born in countries in Asia, Africa, the Caribbean, and Latin
America that have high prevalence of TB;
* persons from medically underserved, low-income populations;
* residents of long-term-care facilities (e.g., correctional
institutions and nursing homes);
* persons from high-risk populations in their communities, as
determined by local public health authorities.
3. An induration of greater than or equal to 15 mm is classified as
positive in persons who do not meet any of the above criteria.
4. Recent converters are defined on the basis of both size of induration
and age of the person being tested:
* Greater than or equal to 10 mm increase within a 2-year period is
classified as a recent conversion for persons less than or equal to
35 years of age;
* Greater than or equal to 15 mm increase within a 2-year period is
classified as a recent conversion for persons greater than or equal
to 35 years of age.
5. PPD skin-test results in health-care workers (HCWs)
* In general, the recommendations in sections 1, 2, and 3 of this
table should be followed when interpreting skin-test results in
HCWs.
* However, the prevalence of TB in the facility should be considered
when choosing the appropriate cut-point for defining a positive PPD
reaction. In facilities where there is essentially no risk for
exposure to Mycobacterium tuberculosis (i.e., minimal- or very
low-risk facilities [Section II.B]), an induration greater than or
equal 15 mm may be a suitable cut-point for HCWs who have no other
risk factors. In facilities where TB patients receive care, the
cut-pint for HCWs with no other risk factors may be greater than or
equal 10 mm.
* A recent conversion in an HCW should be defined generally as a
greater than or equal to 10 mm increase in size of induration within
a 2-year period. For HCWs who work in facilities where exposure to
TB is very unlikely (e.g., minimal-risk facilities), an increase of
greater than or equal to 15 mm within a 2-year period may be more
appropriate for defining a recent conversion because of the lower
positive-predictive value of the test in such groups.
____________________________________________________________________________
5. BCG vaccination and PPD skin testing
BCG vaccination may produce a PPD reaction that cannot be
distinguished reliably from a reaction caused by infection
with M. tuberculosis. For a person who was vaccinated with
BCG, the probability that a PPD test reaction results from
infection with M. tuberculosis increases a) as the size of
the reaction increases, b) when the person is a contact of
a person with TB, c) when the person's country of origin
has a high prevalence of TB, and d) as the length of time
between vaccination and PPD testing increases. For example,
a PPD test reaction of greater than or equal to 10 mm
probably can be attributed to M. tuberculosis infection in
an adult who was vaccinated with BCG as a child and who is
from a country with a high prevalence of TB (74,75).
6. The booster phenomenon
The ability of persons who have TB infection to react to
PPD may gradually wane. For example, if tested with PPD,
adults who were infected during their childhood may have a
negative reaction. However, the PPD could boost the
hypersensitivity, and the size of the reaction could be
larger on a subsequent test. This boosted reaction may be
misinterpreted as a PPD test conversion from a newly
acquired infection. Misinterpretation of a boosted reaction
as a new infection could result in unnecessary
investigations of laboratory and patient records in an
attempt to identify the source case and in unnecessary
prescription of preventive therapy for HCWs. Although
boosting can occur among persons in any age group, the
likelihood of the reaction increases with the age of the
person being tested (6,76).
When PPD testing of adults is to be repeated periodically
(as in HCW skin-testing programs), two-step testing can be
used to reduce the likelihood that a boosted reaction is
misinterpreted as a new infection. Two-step testing should
be performed on all newly employed HCWs who have an initial
negative PPD test result at the time of employment and have
not had a documented negative PPD test result during the 12
months preceding the initial test. A second test should be
performed 1-3 weeks after the first test. If the second
test result is positive, this is most likely a boosted
reaction, and the HCW should be classified as previously
infected. If the second test result remains negative, the
HCW is classified as uninfected, and a positive reaction to
a subsequent test is likely to represent a new infection
with M. tuberculosis.
B. Chest Radiography
Patients who have positive skin-test results or symptoms
suggestive of TB should be evaluated with a chest radiograph
regardless of PPD test results. Radiographic abnormalities that
strongly suggest active TB include upper-lobe infiltration,
particularly if cavitation is seen (77), and patchy or nodular
infiltrates in the apical or subapical posterior upper lobes or
the superior segment of the lower lobe. If abnormalities are
noted, or if the patient has symptoms suggestive of
extrapulmonary TB, additional diagnostic tests should be
conducted.
The radiographic presentation of pulmonary TB in HIV-infected
patients may be unusual (78). Typical apical cavitary disease is
less common among such patients. They may have infiltrates in any
lung zone, a finding that is often associated with mediastinal
and/or hilar adenopathy, or they may have a normal chest
radiograph, although this latter finding occurs rarely.
C. Bacteriology
Smear and culture examination of at least three sputum specimens
collected on different days is the main diagnostic procedure for
pulmonary TB (6). Sputum smears that fail to demonstrate AFB do
not exclude the diagnosis of TB. In the United States,
approximately 60% of patients with positive sputum cultures have
positive AFB sputum smears. HIV-infected patients who have
pulmonary TB may be less likely than immunocompetent patients to
have AFB present on sputum smears, which is consistent with the
lower frequency of cavitary pulmonary disease observed among
HIV-infected persons (39,41).
Specimens for smear and culture should contain an adequate
amount of expectorated sputum but not much saliva. If a
diagnosis of TB cannot be established from sputum, a
bronchoscopy may be necessary (36,37). In young children who
cannot produce an adequate amount of sputum, gastric aspirates
may provide an adequate specimen for diagnosis.
A culture of sputum or other clinical specimen that contains M.
tuberculosis provides a definitive diagnosis of TB. Conventional
laboratory methods may require 4-8 weeks for species
identification; however, the use of radiometric culture
techniques and nucleic acid probes facilitates more rapid
detection and identification of mycobacteria (79,80). Mixed
mycobacterial infection, either simultaneous or sequential, can
obscure the identification of M. tuberculosis during the
clinical evaluation and the laboratory analysis (42). The use of
nucleic acid probes for both M. avium complex and M.
tuberculosis may be useful for identifying mixed mycobacterial
infections in clinical specimens.
II. Preventive Therapy for Latent TB Infection and Treatment of Active TB
A. Preventive Therapy for Latent TB Infection
Determining whether a person with a positive PPD test reaction
or conversion is a candidate for preventive therapy must be
based on a) the likelihood that the reaction represents true
infection with M. tuberculosis (as determined by the
cut-points), b) the estimated risk for progression from latent
infection to active TB, and c) the risk for hepatitis associated
with taking isoniazid (INH) preventive therapy (as determined by
age and other factors).
HCWs with positive PPD test results should be evaluated for
preventive therapy regardless of their ages if they a) are
recent converters, b) are close contacts of persons who have
active TB, c) have a medical condition that increases the risk
for TB, d) have HIV infection, or e) use injecting drugs (5).
HCWs with positive PPD test results who do not have these risk
factors should be evaluated for preventive therapy if they are
less than 35 years of age.
Preventive therapy should be considered for anergic persons who are
known contacts of infectious TB patients and for persons from
populations in which the prevalence of TB infection is very high
(e.g., a prevalence of greater than 10%).
Because the risk for INH-associated hepatitis may be increased
during the peripartum period, the decision to use preventive therapy
during pregnancy should be made on an individual basis and should
depend on the patient's estimated risk for progression to active
disease. In general, preventive therapy can be delayed until after
delivery. However, for pregnant women who were probably infected
recently or who have high-risk medical conditions, especially HIV
infection, INH preventive therapy should begin when the infection is
documented (81-84). No evidence suggests that INH poses a
carcinogenic risk to humans (85-87).
The usual preventive therapy regimen is oral INH 300 mg daily
for adults and 10 mg/kg/day for children (88). The recommended
duration of therapy is 12 months for persons with HIV infection
and 9 months for children. Other persons should receive INH
therapy for 6-12 months. For persons who have silicosis or a
chest radiograph demonstrating inactive fibrotic lesions and who
have no evidence of active TB, acceptable regimens include a) 4
months of INH plus rifampin or b) 12 months of INH, providing
that infection with INH-resistant organisms is unlikely (33).
For persons likely to be infected with MDR-TB, alternative
multidrug preventive therapy regimens should be considered (89).
All persons placed on preventive therapy should be educated
regarding the possible adverse reactions associated with INH
use, and they should be questioned carefully at monthly
intervals by qualified personnel for signs or symptoms
consistent with liver damage or other adverse effects
(81-84,88,90,91). Because INH-associated hepatitis occurs more
frequently among persons greater than 35 years of age, a
transaminase measurement should be obtained from persons in this
age group before initiation of INH therapy and then obtained
monthly until treatment has been completed. Other factors
associated with an increased risk for hepatitis include daily
alcohol use, chronic liver disease, and injecting-drug use. In
addition, postpubertal black and Hispanic women may be at
greater risk for hepatitis or drug interactions (92). More
careful clinical monitoring of persons with these risk factors
and possibly more frequent laboratory monitoring should be
considered. If any of these tests exceeds three to five times
the upper limit of normal, discontinuation of INH should be
strongly considered. Liver function tests are not a substitute
for monthly clinical evaluations or for the prompt assessment of
signs or symptoms of adverse reactions that could occur between
the regularly scheduled evaluations (33).
Persons who have latent TB infection should be advised that they
can be reinfected with another strain of M. tuberculosis (93).
B. Treatment of Patients Who Have Active TB
Drug-susceptibility testing should be performed on all initial
isolates from patients with TB. However, test results may not be
available for several weeks, making selection of an initial regimen
difficult, especially in areas where drug-resistant TB has been
documented. Current recommendations for therapy and dosage schedules
for the treatment of drug-susceptible TB should be followed (Table
S2-2) (43). Streptomycin is contraindicated in the treatment of
pregnant women because of the risk for ototoxicity to the fetus. In
geographic areas or facilities in which drug-resistant TB is highly
prevalent, the initial treatment regimen used while results of
drug-susceptibility tests are pending may need to be expanded. This
decision should be based on analysis of surveillance data.
When results from drug-susceptibility tests become available,
the regimen should be adjusted appropriately (94-97). If drug
resistance is present, clinicians unfamiliar with the management of
patients with drug-resistant TB should seek expert consultation.
For any regimen to be effective, adherence to the regimen must be
ensured. The most effective method of ensuring adherence is the use
of DOT after the patient has been discharged from the hospital
(43,91). This practice should be coordinated with the public
health department.
(For Table S2-2, see printed copy)
(For Table S2-3, see printed copy)
Supplement 3: Engineering Controls
I. Introduction
This supplement provides information regarding the use of ventilation
(Section II) and UVGI (Section III) for preventing the transmission of
M. tuberculosis in health-care facilities. The information provided is
primarily conceptual and is intended to educate staff in the health-care
facility concerning engineering controls and how these controls can be
used as part of the TB infection-control program. This supplement should
not be used in place of consultation with experts, who can assume
responsibility for advising on ventilation system design and
selection, installation, and maintenance of equipment.
The recommendations for engineering controls include a) local exhaust
ventilation (i.e., source control), b) general ventilation, and c) air
cleaning. General ventilation considerations include a) dilution and
removal of contaminants, b) airflow patterns within rooms, c) airflow
direction in facilities, d) negative pressure in rooms, and e) TB
isolation rooms. Air cleaning or disinfection can be accomplished by
filtration of air (e.g., through HEPA filters) or by UVGI.
II. Ventilation
Ventilation systems for health-care facilities should be designed, and
modified when necessary, by ventilation engineers in collaboration with
infection-control and occupational health staff. Recommendations for
designing and operating ventilation systems have been published by ASHRAE
(47), AIA (48), and the American Conference of Governmental Industrial
Hygienists, Inc. (98).
As part of the TB infection-control plan, health-care facility personnel
should determine the number of TB isolation rooms, treatment rooms, and
local exhaust devices (i.e., for cough-inducing or aerosol-generating
procedures) that the facility needs. The locations of these rooms and
devices will depend on where in the facility the ventilation conditions
recommended in this document can be achieved. Grouping isolation rooms
together in one area of the facility may facilitate the care of TB
patients and the installation and maintenance of optimal engineering
controls (particularly ventilation).
Periodic evaluations of the ventilation system should review the number
of TB isolation rooms, treatment rooms, and local exhaust devices needed
and the regular maintenance and monitoring of the local and general
exhaust systems (including HEPA filtration systems if they are used).
The various types and conditions of ventilation systems in health-care
facilities and the individual needs of these facilities preclude the
ability to provide specific instructions regarding the implementation of
these recommendations. Engineering control methods must be tailored to
each facility on the basis of need and the feasibility of using the
ventilation and air-cleaning concepts discussed in this supplement.
A. Local Exhaust Ventilation
Purpose: To capture airborne contaminants at or near their source
(i.e., the source control method) and remove these contaminants
without exposing persons in the area to infectious agents (98).
Source control techniques can prevent or reduce the spread of
infectious droplet nuclei into the general air circulation by
entrapping infectious droplet nuclei as they are being emitted by
the patient (i.e., the source). These techniques are especially
important when performing procedures likely to generate aerosols
containing infectious particles and when infectious TB patients are
coughing or sneezing.
Local exhaust ventilation is a preferred source control technique,
and it is often the most efficient way to contain airborne such as
leukemias and lymphomas; and other source before they can disperse.
Therefore, the technique should be used, if feasible, wherever
aerosol-generating procedures are performed. Two basic types of
local exhaust devices use hoods: a) the enclosing type, in which
the hood either partially or fully encloses the infectious
source; and b) the exterior type, in which the infectious source
is near but outside the hood. Fully enclosed hoods, booths, or
tents are always preferable to exterior types because of their
superior ability to prevent contaminants from escaping into the
HCW's breathing zone. Descriptions of both enclosing and exterior
devices have been published previously (98).
1. Enclosing devices
The enclosing type of local exhaust ventilation device includes
laboratory hoods used for processing specimens that could
contain viable infectious organisms, booths used for sputum
induction or administration of aerosolized medications (e.g.,
aerosolized pentamidine) (Figure S3-1), and tents or hoods made
of vinyl or other materials used to enclose and isolate a patient.
These devices are available in various configurations. The most
simple of these latter devices is a tent that is placed over
the patient; the tent has an exhaust connection to the room
discharge exhaust system. The most complex device is an enclosure
that has a sophisticated self-contained airflow and recirculation
system.
Both tents and booths should have sufficient airflow to remove at
least 99% of airborne particles during the interval between the
departure of one patient and the arrival of the next (99). The
time required for removing a given percentage of airborne
particles from an enclosed space depends on several factors.
These factors include the number of ACH, which is determined by
the number of cubic feet of air in the room or booth and the
rate at which air is entering the room or booth at the intake
source; the location of the ventilation inlet and outlet; and
the physical configuration of the room or booth (Table S3-1).
TABLE S3-1. Air changes per hour (ACH) and time in minutes required for
removal efficiencies of 90%, 99%, and 99.9% of airborne contaminants*
-----------------------------------------------------------------------------
Minutes required for a removal efficiency of:
---------------------------------------------
ACH 90% 99% 99.9%
-----------------------------------------------------------------------------
1 138 276 414
2 69 138 207
3 46 92 138
4 35 69 104
5 28 55 83
6 23 46 69
7 20 39 59
8 17 35 52
9 15 31 46
10 14 28 41
11 13 25 38
12 12 23 35
13 11 21 32
14 10 20 30
15 9 18 28
16 9 17 26
17 8 16 24
18 8 15 23
19 7 15 22
20 7 14 21
25 6 11 17
30 5 9 14
35 4 8 12
40 3 7 10
45 3 6 9
50 3 6 8
-----------------------------------------------------------------------------
* This table has been adapted from the formula for the rate of purging
airborne contaminats (99). Values have been derived from the formula
t(1) = [In (C(2) divide C(1) + (Q divide V)] x 60, with T(1) = 0 and
C(2) divide C(1) - (removal efficiency divide 100), and where:
t(1) = initial timepoint
C(1) = initial concentration of contaminant
C(2) = final concentration of contaminants
Q = air flow rate (cubic feet per hour)
V = room volume (cubic feet)
Q divide V = ACH
The times given assume perfect mixing of the air within the space (i.e.,
mixing factor = 1). However, perfect mixing usually does not occur, and
the mixing factor could be as high as 10 if air distribution is very poor
(98). The required time is derived by multiplying the appropriate time
from the tale by the mixing factor that has been determined for the booth
or room. The factor and required time should be included in the operating
instructions provided by the manufacturer of the booth or enclosure, and
these instructions should be followed.
2. Exterior devices
The exterior type of local exhaust ventilation device is usually
a hood very near, but not enclosing, the infectious patient. The
airflow produced by these devices should be sufficient to prevent
cross-currents of air near the patient's face from causing escape
of droplet nuclei. Whenever possible, the patient should face
directly into the hood opening so that any coughing or sneezing
is directed into the hood, where the droplet nuclei are captured.
The device should maintain an air velocity of greater than or
equal to 200 feet per minute at the patient's breathing zone to
ensure capture of droplet nuclei.
3. Discharge exhaust from booths, tents, and hoods
Air from booths, tents, and hoods may be discharged into the room
in which the device is located or it may be exhausted to the
outside. If the air is discharged into the room, a HEPA filter
should be incorporated at the discharge duct or vent of the
device. The exhaust fan should be located on the discharge side
of the HEPA filter to ensure that the air pressure in the filter
housing and booth is negative with respect to adjacent areas.
Uncontaminated air from the room will flow into the booth through
all openings, thus preventing infectious droplet nuclei in the
booth from escaping into the room. Most commercially available
booths, tents, and hoods are fitted with HEPA filters, in which
case additional HEPA filtration is not needed.
If the device does not incorporate a HEPA filter, the air from
the device should be exhausted to the outside in accordance with
recommendations for isolation room exhaust (Suppl. 3, Section
II.B.5). (See Supplement 3, Section II.C, for information
regarding recirculation of exhaust air.)
B. General Ventilation
General ventilation can be used for several purposes, including
diluting and removing contaminated air, controlling airflow patterns
within rooms, and controlling the direction of airflow throughout a
facility. Information on these topics is contained in the following
sections.
1. Dilution and removal
Purpose: To reduce the concentration of contaminants in the air.
General ventilation maintains air quality by two processes:
dilution and removal of airborne contaminants. Uncontaminated
supply (i.e., incoming) air mixes with the contaminated room air
(i.e., dilution), which is subsequently removed from the room by
the exhaust system (i.e., removal). These processes reduce the
concentration of droplet nuclei in the room air.
a. Types of general ventilation systems
Two types of general ventilation systems can be used for
dilution and removal of contaminated air: the single-pass
system and the recirculating system. In a single-pass system,
the supply air is either outside air that has been
appropriately heated and cooled or air from a central system
that supplies a number of areas. After air passes through the
room (or area), 100% of that air is exhausted to the outside.
The single-pass system is the preferred choice in areas where
infectious airborne droplet nuclei are known to be present
(e.g., TB isolation rooms or treatment rooms) because it
prevents contaminated air from being recirculated to other
areas of the facility.
In a recirculating system, a small portion of the exhaust
air is discharged to the outside and is replaced with
fresh outside air, which mixes with the portion of exhaust
air that was not discharged to the outside. The resulting
mixture, which can contain a large proportion of
contaminated air, is then recirculated to the areas serviced
by the system. This air mixture could be recirculated into
the general ventilation, in which case contaminants may be
carried from contaminated areas to uncontaminated areas.
Alternatively, the air mixture could also be recirculated
within a specific room or area, in which case other areas of
the facility will not be affected (Suppl. 3, Section II.C.3).
b. Ventilation rates
Recommended general ventilation rates for health-care
facilities are usually expressed in number of ACH. This
number is the ratio of the volume of air entering the room
per hour to the room volume and is equal to the exhaust
airflow (Q [cubic feet per minute]) divided by the room
volume (V [cubic feet]) multiplied by 60 (i.e., ACH = Q /
V x 60).
The feasibility of achieving specific ventilation rates
depends on the construction and operational requirements of
the ventilation system (e.g., the energy requirements to
move and to heat or cool the air). The feasibility of
achieving specific ventilation rates may also be different
for retrofitted facilities and newly constructed facilities.
The expense and effort of achieving specific higher
ventilation rates for new construction may be reasonable,
whereas retrofitting an existing facility to achieve similar
ventilation rates may be more difficult. However, achieving
higher ventilation rates by using auxiliary methods (e.g.,
room-air recirculation) in addition to exhaust ventilation
may be feasible in existing facilities (Suppl. 3, Section
II.C).
2. Airflow patterns within rooms (air mixing)
Purpose: To provide optimum airflow patterns and prevent both
stagnation and short-circuiting of air.
General ventilation systems should be designed to provide
optimal patterns of airflow within rooms and prevent air
stagnation or short-circuiting of air from the supply to the
exhaust (i.e., passage of air directly from the air supply to
the air exhaust). To provide optimal airflow patterns, the air
supply and exhaust should be located such that clean air first
flows to parts of the room where HCWs are likely to work, and
then flows across the infectious source and into the exhaust. In
this way, the HCW is not positioned between the infectious
source and the exhaust location. Although this configuration may
not always be possible, it should be used whenever feasible. One
way to achieve this airflow pattern is to supply air at the side
of the room opposite the patient and exhaust it from the side
where the patient is located. Another method, which is most
effective when the supply air is cooler than the room air, is to
supply air near the ceiling and exhaust it near the floor
(Figure S3-2). Airflow patterns are affected by large air
temperature differentials, the precise location of the supply
and exhausts, the location of furniture, the movement of HCWs
and patients, and the physical configuration of the space. Smoke
tubes can be used to visualize airflow patterns in a manner
similar to that described for estimating room air mixing.
Adequate air mixing, which requires that an adequate number of
ACH be provided to a room (Suppl. 3, Section II.B.1), must be
ensured to prevent air stagnation within the room. However, the
air will not usually be changed the calculated number of times
per hour because the airflow patterns in the room may not permit
complete mixing of the supply and room air in all parts of the
room. This results in an "effective" airflow rate in which the
supplied airflow may be less than required for proper ventilation.
To account for this variation, a mixing factor (which ranges from
1 for perfect mixing to 10 for poor mixing) is applied as a
multiplier to determine the actual supply airflow (i.e., the
recommended ACH multiplied by the mixing factor equals the actual
required ACH) (51,98). The room air supply and exhaust system
should be designed to achieve the lowest mixing factor possible.
The mixing factor is determined most accurately by experimentally
testing each space configuration, but this procedure is complex
and time-consuming. A reasonably good qualitative measure of
mixing can be estimated by an experienced ventilation engineer
who releases smoke from smoke tubes at a number of locations in
the room and observes the movement of the smoke. Smoke movement
in all areas of the room indicates good mixing. Stagnation of air
in some areas of the room indicates poor mixing, and movement of
the supply and exhaust openings or redirection of the supply air
is necessary.
(For Figure S3-2, see printed copy)
3. Airflow direction in the facility
Purpose: To contain contaminated air in localized areas in a
facility and prevent its spread to uncontaminated areas.
a. Directional airflow
The general ventilation system should be designed and
balanced so that air flows from less contaminated (i.e.,
more clean) to more contaminated (less clean) areas (47,48).
For example, air should flow from corridors (cleaner areas)
into TB isolation rooms (less clean areas) to prevent spread
of contaminants to other areas. In some special treatment
rooms in which operative and invasive procedures are
performed, the direction of airflow is from the room to the
hallway to provide cleaner air during these procedures.
Cough-inducing or aerosol-generating procedures (e.g.,
bronchoscopy and irrigation of tuberculous abscesses) should
not be performed in rooms with this type of airflow on
patients who may have infectious TB.
b. Negative pressure for achieving directional airflow
The direction of airflow is controlled by creating a lower
(negative) pressure in the area into which the flow of air
is desired. For air to flow from one area to another, the
air pressure in the two areas must be different. Air will
flow from a higher pressure area to a lower pressure area.
The lower pressure area is described as being at negative*
pressure relative to the higher pressure area. Negative
pressure is attained by exhausting air from an area at a
higher rate than air is being supplied. The level of
negative pressure necessary to achieve the desired airflow
will depend on the physical configuration of the ventilation
system and area, including the airflow path and flow openings,
and should be determined on an individual basis by an
experienced ventilation engineer.
__________
* Negative is defined relative to the air pressure in the area from which
air is to flow.
4. Achieving negative pressure in a room
Purpose: To control the direction of airflow between the room
and adjacent areas, thereby preventing contaminated air from
escaping from the room into other areas of the facility.
a. Pressure differential
The minimum pressure difference necessary to achieve and
maintain negative pressure that will result in airflow into
the room is very small (0.001 inch of water). Higher
pressures ( greater than or equal to 0.001 inch of water)
are satisfactory; however, these higher pressures may be
difficult to achieve. The actual level of negative pressure
achieved will depend on the difference in the ventilation
exhaust and supply flows and the physical configuration of
the room, including the airflow path and flow openings. If
the room is well sealed, negative pressures greater than the
minimum of 0.001 inch of water may be readily achieved.
However, if rooms are not well sealed, as may be the case in
many facilities (especially older facilities), achieving
higher negative pressures may require exhaust/supply flow
differentials beyond the capability of the ventilation
system.
To establish negative pressure in a room that has a normally
functioning ventilation system, the room supply and exhaust
airflows are first balanced to achieve an exhaust flow of
either 10% or 50 cubic feet per minute (cfm) greater than
the supply (whichever is the greater). In most situations,
this specification should achieve a negative pressure of at
least 0.001 inch of water. If the minimum 0.001 inch of
water is not achieved and cannot be achieved by increasing
the flow differential (within the limits of the ventilation
system), the room should be inspected for leakage (e.g.,
through doors, windows, plumbing, and equipment wall
penetrations), and corrective action should be taken to
seal the leaks.
Negative pressure in a room can be altered by changing the
ventilation system operation or by the opening and closing
of the room's doors, corridor doors, or windows. When an
operating configuration has been established, it is
essential that all doors and windows remain properly closed
in the isolation room and other areas (e.g., doors in
corridors that affect air pressure) except when persons
need to enter or leave the room or area.
b. Alternate methods for achieving negative pressure
Although an anteroom is not a substitute for negative
pressure in a room, it may be used to reduce escape of
droplet nuclei during opening and closing of the isolation
room door. Some anterooms have their own air supply duct,
but others do not. The TB isolation room should have
negative pressure relative to the anteroom, but the air
pressure in the anteroom relative to the corridor may vary
depending on the building design. This should be determined,
in accordance with applicable regulations, by a qualified
ventilation engineer.
If the existing ventilation system is incapable of achieving
the desired negative pressure because the room lacks a
separate ventilation system or the room's system cannot
provide the proper airflow, steps should be taken to provide
a means to discharge air from the room. The amount of air to
be exhausted will be the same as discussed previously (Suppl.
3, Section II.B.4.a).
Fixed room-air recirculation systems (i.e., systems that
recirculate the air in an entire room) may be designed to
achieve negative pressure by discharging air outside the room
(Suppl. 3, Section II.C.3).
Some portable room-air recirculation units (Suppl. 3, Section
II.C.3.b.) are designed to discharge air to the outside to
achieve negative pressure. Air cleaners that can accomplish
this must be designed specifically for this purpose.
A small centrifugal blower (i.e., exhaust fan) can be used to
exhaust air to the outside through a window or outside wall.
This approach may be used as an interim measure to achieve
negative pressure, but it provides no fresh air and
suboptimal dilution.
Another approach to achieving the required pressure
difference is to pressurize the corridor. Using this method,
the corridor's general ventilation system is balanced to
create a higher air pressure in the corridor than in the
isolation room; the type of balancing necessary depends on
the configuration of the ventilation system. Ideally, the
corridor air supply rate should be increased while the
corridor exhaust rate is not increased. If this is not
possible, the exhaust rate should be decreased by resetting
appropriate exhaust dampers. Caution should be exercised,
however, to ensure that the exhaust rate is not reduced
below acceptable levels. This approach requires that all
settings used to achieve the pressure balance, including
doors, be maintained. This method may not be desirable if
the corridor being pressurized has rooms in which negative
pressure is not desired. In many situations, this system is
difficult to achieve, and it should be considered only after
careful review by ventilation personnel.
c. Monitoring negative pressure
The negative pressure in a room can be monitored by
visually observing the direction of airflow (e.g., using
smoke tubes) or by measuring the differential pressure
between the room and its surrounding area.
Smoke from a smoke tube can be used to observe airflow
between areas or airflow patterns within an area. To check
the negative pressure in a room by using a smoke tube, hold
the smoke tube near the bottom of the door and approximately
2 inches in front of the door, or at the face of a grille or
other opening if the door has such a feature, and generate a
small amount of smoke by gently squeezing the bulb (Figure
S3-3). The smoke tube should be held parallel to the door,
and the smoke should be issued from the tube slowly to
ensure the velocity of the smoke from the tube does not
overpower the air velocity. The smoke will travel in the
direction of airflow. If the room is at negative pressure,
the smoke will travel under the door and into the room (e.g.,
from higher to lower pressure). If the room is not at
negative pressure, the smoke will be blown outward or will
stay stationary. This test must be performed while the door
is closed. If room air cleaners are being used in the room,
they should be running. The smoke is irritating if inhaled,
and care should be taken not to inhale it directly from the
smoke tube. However, the quantity of smoke issued from the
tube is minimal and is not detectable at short distances
from the tube.
Differential pressure-sensing devices also can be used to
monitor negative pressure; they can provide either periodic
(noncontinuous) pressure measurements or continuous
pressure monitoring. The continuous monitoring component may
simply be a visible and/or audible warning signal that air
pressure is low. In addition, it may also provide a pressure
readout signal, which can be recorded for later verification
or used to automatically adjust the facility's ventilation
control system.
Pressure-measuring devices should sense the room pressure
just inside the airflow path into the room (e.g., at the
bottom of the door). Unusual airflow patterns within the
room can cause pressure variations; for example, the air can
be at negative pressure at the middle of a door and at
positive pressure at the bottom of the same door (Figure
S-34). If the pressure-sensing ports of the device cannot be
located directly across the airflow path, it will be
necessary to validate that the negative pressure at the
sensing point is and remains the same as the negative
pressure across the flow path.
(For Figure S3-3, see printed copy)
Pressure-sensing devices should incorporate an audible
warning with a time delay to indicate that a door is open.
When the door to the room is opened, the negative pressure
will decrease. The time-delayed signal should allow
sufficient time for persons to enter or leave the room
without activating the audible warning.
A potential problem with using pressure-sensing devices is
that the pressure differentials used to achieve the low
negative pressure necessitate the use of very sensitive
mechanical devices, electronic devices, or pressure gauges
to ensure accurate measurements. Use of devices that cannot
measure these low pressures (i.e., pressures as low as 0.001
inch of water) will require setting higher negative pressures
that may be difficult and, in some instances, impractical to
achieve (Suppl. 3, Section II.B.4).
Periodic checks are required to ensure that the desired
negative pressure is present and that the continuous
monitoring devices, if used, are operating properly. If smoke
tubes or other visual checks are used, TB isolation rooms and
treatment rooms should be checked frequently for negative
pressure. Rooms undergoing changes to the ventilation system
should be checked daily. TB isolation rooms should be checked
daily for negative pressure while being used for TB
isolation. If these rooms are not being used for patients who
have suspected or confirmed TB but potentially could be used
for such patients, the negative pressure in the rooms should
be checked monthly. If pressure-sensing devices are used,
negative pressure should be verified at least once a month
by using smoke tubes or taking pressure measurements.
(For Figure S3-4, see printed copy)
C. HEPA filtration
Purpose: To remove contaminants from the air.
HEPA filtration can be used as a method of air cleaning that
supplements other recommended ventilation measures. For the
purposes of these guidelines, HEPA filters are defined as
air-cleaning devices that have a demonstrated and documented minimum
removal efficiency of 99.97% of particles greater than or equal to
0.3 um in diameter. HEPA filters have been shown to be effective in
reducing the concentration of Aspergillus spores (which range in
size from 1.5 um to 6 um) to below measurable levels (100-102). The
ability of HEPA filters to remove tubercle bacilli from the air has
not been studied, but M. tuberculosis droplet nuclei probably range
from 1 um to 5 um in diameter (i.e., approximately the same size as
Aspergillus spores). Therefore, HEPA filters can be expected to
remove infectious droplet nuclei from contaminated air. HEPA filters
can be used to clean air before it is exhausted to the outside,
recirculated to other areas of a facility, or recirculated within a
room. If the device is not completely passive (e.g., it utilizes
techniques such as electrostatics) and the failure of the
electrostatic components permits loss of filtration efficiency to
less than 99.97%, the device should not be used in systems that
recirculate air back into the general facility ventilation system
from TB isolation rooms and treatment rooms in which procedures are
performed on patients who may have infectious TB (Suppl. 3, Section
II.C.2).
HEPA filters can be used in a number of ways to reduce or eliminate
infectious droplet nuclei from room air or exhaust. These methods
include placement of HEPA filters a) in exhaust ducts to remove
droplet nuclei from air being discharged to the outside, either
directly or through ventilation equipment; b) in ducts discharging
room air into the general ventilation system; and c) in fixed or
portable room-air cleaners. The effectiveness of portable HEPA
room-air cleaning units has not been evaluated adequately, and there
is probably considerable variation in their effectiveness. HEPA
filters can also be used in exhaust ducts or vents that discharge
air from booths or enclosures into the surrounding room (Suppl. 3,
Section II.A.3). In any application, HEPA filters should be
installed carefully and maintained meticulously to ensure adequate
function.
Manufacturers of room-air cleaning equipment should provide
documentation of the HEPA filter efficiency and the efficiency of
the installed device in lowering room-air contaminant levels.
1. Use of HEPA filtration when exhausting air to the outside
HEPA filters can be used as an added safety measure to clean air
from isolation rooms and local exhaust devices (i.e., booths,
tents, or hoods used for cough-inducing procedures) before
exhausting it directly to the outside, but such use is
unnecessary if the exhaust air cannot re-enter the ventilation
system supply. The use of HEPA filters should be considered
wherever exhaust air could possibly reenter the system.
In many instances, exhaust air is not discharged directly to the
outside; rather, the air is directed through heat-recovery
devices (e.g., heat wheels). Heat wheels are often used to reduce
the costs of operating ventilation systems (103). If such units
are used with the system, a HEPA filter should also be used. As
the wheel rotates, energy is transferred into or removed from the
supply inlet air stream. The HEPA filter should be placed
upstream from the heat wheel because of the potential for leakage
across the seals separating the inlet and exhaust chambers and
the theoretical possibility that droplet nuclei could be
impacted on the wheel by the exhaust air and subsequently
stripped off into the supply air.
2. Recirculation of HEPA-filtered air to other areas of a facility
Air from TB isolation rooms and treatment rooms used to treat
patients who have confirmed or suspected infectious TB should
be exhausted to the outside in accordance with applicable
federal, state, and local regulations. The air should not be
recirculated into the general ventilation. In some instances,
recirculation of air into the general ventilation system from
such rooms is unavoidable (i.e., in existing facilities in which
the ventilation system or facility configuration makes venting
the exhaust to the outside impossible). In such cases, HEPA
filters should be installed in the exhaust duct leading from the
room to the general ventilation system to remove infectious
organisms and particulates the size of droplet nuclei from the
air before it is returned to the general ventilation system
(Section II.F; Suppl. 3). Air from TB isolation rooms and
treatment rooms in new or renovated facilities should not be
recirculated into the general ventilation system.
3. Recirculation of HEPA-filtered air within a room
Individual room-air recirculation can be used in areas where
there is no general ventilation system, where an existing system
is incapable of providing adequate airflow, or where an increase
in ventilation is desired without affecting the fresh air supply
or negative pressure system already in place. Recirculation of
HEPA-filtered air within a room can be achieved in several ways:
a) by exhausting air from the room into a duct, filtering it
through a HEPA filter installed in the duct, and returning it to
the room (Figure S3-5); b) by filtering air through HEPA
recirculation systems mounted on the wall or ceiling of the room
(Figure S3-6); or c) by filtering air through portable HEPA
recirculation systems. In this document, the first two of these
approaches are referred to as fixed room-air recirculation
systems, because the HEPA filter devices are fixed in place and
are not easily movable.
(For Figure S3-5, see printed copy)
(For Figure S3-6, see printed copy)
a. Fixed room-air recirculation systems
The preferred method of recirculating HEPA-filtered air
within a room is a built-in system, in which air is
exhausted from the room into a duct, filtered through a HEPA
filter, and returned to the room (Figure S3-5). This
technique may be used to add air changes in areas where
there is a recommended minimum ACH that is difficult to meet
with general ventilation alone. The air does not have to be
conditioned, other than by the filtration, and this permits
higher airflow rates than the general ventilation system can
usually achieve. An alternative is the use of HEPA filtration
units that are mounted on the wall or ceiling of the room
(Figure S3-7). Fixed recirculation systems are preferred over
portable (free-standing) units because they can be installed
and maintained with a greater degree of reliability.
b. Portable room-air recirculation units
Portable HEPA filtration units may be considered for
recirculating air within rooms in which there is no general
ventilation system, where the system is incapable of
providing adequate airflow, or where increased effectiveness
in room airflow is desired. Effectiveness depends on
circulating as much of the air in the room as possible
through the HEPA filter, which may be difficult to achieve
and evaluate. The effectiveness of a particular unit can
vary depending on the room's configuration, the furniture
and persons in the room, and placement of the HEPA filtration
unit and the supply and exhaust grilles. Therefore, the
effectiveness of the portable unit may vary considerably in
rooms with different configurations or in the same room if
moved from one location to another in the room. If portable
units are used, caution should be exercised to ensure they
can recirculate all or nearly all of the room air through
the HEPA filter. Some commercially available units may not
be able to meet this requirement because of design
limitations or insufficient airflow capacity. In addition,
units should be designed and operated to ensure that persons
in the room cannot interfere with or otherwise compromise
the functioning of the unit. Portable HEPA filtration units
have not been evaluated adequately to determine their role
in TB infection-control programs.
Portable HEPA filtration units should be designed to achieve
the equivalent of greater than or equal to 12 ACH. They
should also be designed to ensure adequate air mixing in all
areas of the hospital rooms in which they are used, and they
should not interfere with the current ventilation system.
Some HEPA filtration units employ UVGI for disinfecting air
after HEPA filtration. However, whether exposing the
HEPA-filtered air to UV irradiation further decreases the
concentration of contaminants is not known.
c. Evaluation of room-air recirculation systems and units
Detailed and accurate evaluations of room-air recirculation
systems and units require the use of sophisticated test
equipment and lengthy test procedures that are not practical.
However, an estimate of the unit's ability to circulate the
air in the room can be made by visualizing airflow patterns
as was described previously for estimating room air mixing
(Suppl. 3, Section II.B.1). If the air movement is good in
all areas of the room, the unit should be effective.
4. Installing, maintaining, and monitoring HEPA filters
Proper installation and testing and meticulous maintenance are
critical if a HEPA filtration system is used (104), especially
if the system used recirculates air to other parts of the
facility. Improper design, installation, or maintenance could
allow infectious particles to circumvent filtration and escape
into the general ventilation system (47). HEPA filters should
be installed to prevent leakage between filter segments and
between the filter bed and its frame. A regularly scheduled
maintenance program is required to monitor the HEPA filter for
possible leakage and for filter loading. A quantitative leakage
and filter performance test (e.g., the dioctal phthalate [DOP]
penetration test [105]) should be performed at the initial
installation and every time the filter is changed or moved. The
test should be repeated every 6 months for filters in general-use
areas and in areas with systems that exhaust air that is likely
to be contaminated with M. tuberculosis (e.g, TB isolation rooms).
A manometer or other pressure-sensing device should be installed
in the filter system to provide an accurate and objective means
of determining the need for filter replacement. Pressure drop
characteristics of the filter are supplied by the manufacturer
of the filter. Installation of the filter should allow for
maintenance that will not contaminate the delivery system or the
area served. For general infection-control purposes, special care
should be taken to not jar or drop the filter element during or
after removal.
The scheduled maintenance program should include procedures for
installation, removal, and disposal of filter elements. HEPA
filter maintenance should be performed only by adequately trained
personnel. Appropriate respiratory protection should be worn
while performing maintenance and testing procedures. In addition,
filter housing and ducts leading to the housing should be
labelled clearly with the words "Contaminated Air" (or a similar
warning).
When a HEPA filter is used, one or more lower efficiency
disposable prefilters installed upstream will extend the useful
life of the HEPA filter. A disposable filter can increase the
life of a HEPA filter by 25%. If the disposable filter is
followed by a 90% extended surface filter, the life of the HEPA
filter can be extended almost 900% (98). These prefilters should
be handled and disposed of in the same manner as the HEPA filter.
D. TB Isolation Rooms and Treatment Rooms
Purpose: To separate patients who are likely to have infectious TB
from other persons, to provide an environment that will allow
reduction of the concentration of droplet nuclei through various
engineering methods, and to prevent the escape of droplet nuclei
from such rooms into the corridor and other areas of the facility
using directional airflow.
A hierarchy of ventilation methods used to achieve a reduction in
the concentration of droplet nuclei and to achieve directional
airflow using negative pressure has been developed (Table S3-2).
The methods are listed in order from the most desirable to the least
desirable. The method selected will depend on the configuration of
the isolation room and the ventilation system in the facility; the
determination should be made in consultation with a ventilation
engineer.
(For Table S3-2, see printed copy)
1. Preventing the escape of droplet nuclei from the room
Rooms used for TB isolation should be single-patient rooms with
negative pressure relative to the corridor or other areas
connected to the room. Doors between the isolation room and
other areas should remain closed except for entry into or exit
from the room. The room's openings (e.g., windows and electrical
and plumbing entries) should be sealed as much as possible.
However, a small gap of 1/8 to 1/2 inch should be at the bottom
of the door to provide a controlled airflow path. Proper use of
negative pressure will prevent contaminated air from escaping
the room.
2. Reducing the concentration of droplet nuclei in the room
ASHRAE (47), AIA (48), and the Health Resources and Services
Administration (49) recommend a minimum of 6 ACH for TB isolation
rooms and treatment rooms. This ventilation rate is based on
comfort- and odor-control considerations. The effectiveness of
this level of airflow in reducing the concentration of droplet
nuclei in the room, thus reducing the transmission of airborne
pathogens, has not been evaluated directly or adequately.
Ventilation rates greater than 6 ACH are likely to produce an
incrementally greater reduction in the concentration of bacteria
in a room than are lower rates (50-52). However, accurate
quantitation of decreases in risk that would result from
specific increases in general ventilation levels has not been
performed and may not be possible.
To reduce the concentration of droplet nuclei, TB isolation rooms
and treatment rooms in existing health-care facilities should
have an airflow of greater than or equal to 6 ACH. Where feasible,
this airflow rate should be increased to greater than or equal to
12 ACH by adjusting or modifying the ventilation system or by
using auxiliary means (e.g., recirculation of air through fixed
HEPA filtration units or portable air cleaners) (Suppl. 3,
Section II.C) (53). New construction or renovation of existing
health-care facilities should be designed so that TB isolation
rooms achieve an airflow of greater than or equal to 12 ACH.
3. Exhaust from TB isolation rooms and treatment rooms
Air from TB isolation rooms and treatment rooms in which
patients with infectious TB may be examined should be exhausted
directly to the outside of the building and away from air-intake
vents, persons, and animals in accordance with federal, state,
and local regulations concerning environmental discharges. (See
Suppl. 3, Section II.C, for information regarding recirculation
of exhaust air.) Exhaust ducts should not be located near areas
that may be populated (e.g., near sidewalks or windows that could
be opened). Ventilation system exhaust discharges and inlets
should be designed to prevent reentry of exhausted air. Wind
blowing over a building creates a highly turbulent recirculation
zone, which can cause exhausted air to reenter the building
(Figure S3-7). Exhaust flow should be discharged above this zone
(Suppl. 3, Section II.C.1). Design guidelines for proper
placement of exhaust ducts can be found in the 1989 ASHRAE
Fundamentals Handbook (106). If recirculation of air from such
rooms into the general ventilation system is unavoidable, the
air should be passed through a HEPA filter before recirculation
(Suppl. 3, Section II.C.2).
4. Alternatives to TB isolation rooms
Isolation can also be achieved by use of negative-pressure
enclosures (e.g, tents or booths) (Suppl. 3, Section II.A.1).
These can be used to provide patient isolation in areas such as
emergency rooms and medical testing and treatment areas and to
supplement isolation in designated isolation rooms.
III. UVGI
Purpose: To kill or inactivate airborne tubercle bacilli.
Research has demonstrated that UVGI is effective in killing or
inactivating tubercle bacilli under experimental conditions (66,107-110)
and in reducing transmission of other infections in hospitals (111),
military housing (112), and classrooms (113-115). Because of the results
of numerous studies (116-120) and the experiences of TB clinicians and
mycobacteriologists during the past several decades, the use of UVGI has
been recommended as a supplement to other TB infection-control
measures in settings where the need for killing or inactivating
tubercle bacilli is important (2,4,121-125).
(For Figure S3-7, see printed copy)
UV radiation is defined as that portion of the electromagnetic
spectrum described by wavelengths from 100 to 400 nm. For convenience
of classification, the UV spectrum has been separated into three
different wave-length bands: UV-A (long wavelengths, range: 320-400
nm), UV-B (midrange wavelengths, range: 290-320 nm), and UV-C (short
wavelengths, range: 100-290 nm) (126). Commercially available UV lamps
used for germicidal purposes are low-pressure mercury vapor lamps (127)
that emit radiant energy in the UV-C range, predominantly at a
wavelength of 253.7 nm (128).
A. Applications
UVGI can be used as a method of air disinfection to supplement
other engineering controls. Two systems of UVGI can be used for
this purpose: duct irradiation and upper-room air irradiation.
1. Duct irradiation
Purpose: To inactivate tubercle bacilli without exposing
persons to UVGI.
In duct irradiation systems, UV lamps are placed inside ducts
that remove air from rooms to disinfect the air before it is
recirculated. When UVGI duct systems are properly designed,
installed, and maintained, high levels of UV radiation may be
produced in the duct work. The only potential for human exposure
to this radiation occurs during maintenance operations.
Duct irradiation may be used:
* In a TB isolation room or treatment room to recirculate air
from the room, through a duct containing UV lamps, and back
into the room. This recirculation method can increase the
overall room airflow but does not increase the supply of
fresh outside air to the room.
* In other patients' rooms and in waiting rooms, emergency
rooms, and other general-use areas of a facility where
patients with undiagnosed TB could potentially contaminate
the air, to recirculate air back into the general
ventilation.
Duct-irradiation systems are dependent on airflow patterns
within a room that ensure that all or nearly all of the room
air circulates through the duct.
2. Upper-room air irradiation
Purpose: To inactivate tubercle bacilli in the upper part of
the room, while minimizing radiation exposure to persons in
the lower part of the room.
In upper-room air irradiation, UVGI lamps are suspended from the
ceiling or mounted on the wall. The bottom of the lamp is
shielded to direct the radiation upward but not downward. The
system depends on air mixing to take irradiated air from the
upper to the lower part of the room, and nonirradiated air
from the lower to the upper part. The irradiated air space is
much larger than that in a duct system.
UVGI has been effective in killing bacteria under conditions
where air mixing was accomplished mainly by convection. For
example, BCG was atomized in a room that did not have
supplemental ventilation (120), and in another study a
surrogate bacteria, Serratia marcesens, was aerosolized in a
room with a ventilation rate of 6 ACH (129). These reports
estimated the effect of UVGI to be equivalent to 10 and 39 ACH,
respectively, for the organisms tested, which are less resistant
to UVGI than M. tuberculosis (120). The addition of fans or
some heating/air conditioning arrangements may double the
effectiveness of UVGI lamps (130-132). Greater rates of
ventilation, however, may decrease the length of time the air is
irradiated, thus decreasing the killing of bacteria (117,129).
The optimal relationship between ventilation and UVGI is not
known. Air irradiation lamps used in corridors have been
effective in killing atomized S. marcesens (133). Use of UVGI
lamps in an outpatient room has reduced culturable airborne
bacteria by 14%-19%. However, the irradiation did not reduce the
concentration of gram-positive, rod-shaped bacteria; although
fast-growing mycobacteria were cultured, M. tuberculosis could
not be recovered from the room's air samples because of fungal
over-growth of media plates (134).
Upper-room air UVGI irradiation may be used:
* In isolation or treatment rooms as a supplemental method
of air cleaning.
* In other patients' rooms and in waiting rooms, emergency
rooms, corridors, and other central areas of a facility
where patients with undiagnosed TB could potentially
contaminate the air.
Determinants of UVGI effectiveness include room
configuration, UV lamp placement, and the adequacy of
airflow patterns in bringing contaminated air into contact
with the irradiated upper-room space. Air mixing may be
facilitated by supplying cool air near the ceiling in
rooms where warmer air (or a heating device) is present
below. The ceiling should be high enough for a large
volume of upper-room air to be irradiated without HCWs and
patients being overexposed to UV radiation.
B. Limitations
Because the clinical effectiveness of UV systems varies, and
because of the risk for transmission of M. tuberculosis if a system
malfunctions or is maintained improperly, UVGI is not recommended
for the following specific applications:
1. Duct systems using UVGI are not recommended as a substitute for
HEPA filters if air from isolation rooms must be recirculated to
other areas of a facility.
2. UVGI alone is not recommended as a substitute for HEPA
filtration or local exhaust of air to the outside from booths,
tents, or hoods used for cough-inducing procedures.
3. UVGI is not a substitute for negative pressure.
The use of UV lamps and HEPA filtration in a single unit would
not be expected to have any infection-control benefits not
provided by use of the HEPA filter alone.
The effectiveness of UVGI in killing airborne tubercle bacilli
depends on the intensity of UVGI, the duration of contact the
organism has with the irradiation, and the relative humidity
(66,108,111). Humidity can have an adverse effect on UVGI
effectiveness at levels greater than 70% relative humidity for S.
marcescens (135). The interaction of these factors has not been
fully defined, however, making precise recommendations for
individual UVGI installations difficult to develop.
Old lamps or dust-covered UV lamps are less effective; therefore,
regular maintenance of UVGI systems is crucial.
C. Safety Issues
Short-term overexposure to UV radiation can cause erythema and
keratoconjunctivitis (136,137). Broad-spectrum UV radiation has been
associated with increased risk for squamous and basal cell
carcinomas of the skin (138). UV-C was recently classified by the
International Agency for Research on Cancer as "probably
carcinogenic to humans (Group 2A)" (138). This classification is
based on studies suggesting that UV-C radiation can induce skin
cancers in animals; DNA damage, chromosomal aberrations and sister
chromatid exchange and transformation in human cells in vitro;
and DNA damage in mammalian skin cells in vivo. In the animal
studies, a contribution of UV-B to the tumor effects could not be
excluded, but the effects were greater than expected for UV-B
alone (138). Although some recent studies have demonstrated that UV
radiation can activate HIV gene promoters (i.e., the genes in HIV
that prompt replication of the virus) in laboratory samples of
human cells (139-144), the implications of these in vitro
findings for humans are unknown.
In 1972, the National Institute for Occupational Safety and
Health (NIOSH) published a recommended exposure limit (REL) for
occupational exposure to UV radiation (136). The REL is intended to
protect workers from the acute effects of UV exposure (e.g.,
erythema and photokeratoconjunctivitis). However, photosensitive
persons and those exposed concomitantly to photoactive chemicals
may not be protected by the recommended standard.
If proper procedures are not followed, HCWs performing
maintenance on such fixtures are at risk for exposure to UV
radiation. Because UV fixtures used for upper-room air
irradiation are present in rooms, rather than hidden in ducts,
safety may be much more difficult to achieve and maintain.
Fixtures must be designed and installed to ensure that UV
exposure to persons in the room (including HCWs and inpatients)
are below current safe exposure levels. Recent health hazard
evaluations conducted by CDC have noted problems withover-exposure
of HCWs to UVGI and with inadequate maintenance, training,
labelling, and use of personal protective equipment (145-147).
The current number of persons who are properly trained in UVGI
system design and installation is limited. CDC strongly
recommends that a competent UVGI system designer be consulted to
address safety considerations before such a system is procured and
installed. Experts who might be consulted include industrial
hygienists, engineers, and health physicists. Principles for the
safe installation of UV lamp fixtures have been developed and can
be used as guidelines (148,149).
If UV lamps are being used in a facility, the general TB
education of HCWs should include:
1. The basic principles of UVGI systems (i.e., how they work
and what their limitations are).
2. The potential hazardous effects of UVGI if overexposure
occurs.
3. The potential for photosensitivity associated with certain
medical conditions or use of some medications.
4. The importance of general maintenance procedures for UVGI
fixtures.
Exposure to UV intensities above the REL should be avoided.
Lightweight clothing made of tightly woven fabric and
UV-absorbing sunscreens with solar-protection factors (SPFs)
greater than or equal to 15 may help protect photosensitive
persons. HCWs should be advised that any eye or skin irritation
that develops after UV exposure should be examined by
occupational health staff.
D. Exposure Criteria for UV Radiation
The NIOSH REL for UV radiation is wavelength dependent because
different wavelengths of UV radiation have different adverse
effects on the skin and eyes (136). Relative spectral
effectiveness (S lambda) is used to compare various UV sources
with a source producing UV radiation at 270 nm, the wavelength of
maximum ocular sensitivity. For example, the S lambda at 254 nm
is 0.5; therefore, twice as much energy is required at 254 nm to
produce an identical biologic effect at 270 nm (136). Thus, at
254 nm, the NIOSH REL is 0.006 joules per square centimeter
(J/cm(2)); and at 270 nm, it is 0.003 J/cm(2).
For germicidal lamps that emit radiant energy predominantly at a
wavelength of 254 nm, proper use of the REL requires that the
measured irradiance level (E) in microwatts per square centimeter
(uW/cm(2)) be multiplied by the relative spectral effectiveness at
254 nm (0.5) to obtain the effective irradiance (E(eff)). The
maximum permissible exposure time can then be determined for
selected values of E(eff) (Table S3-3), or it can be calculated (in
seconds) by dividing 0.003 J/cm(2) (the NIOSH REL at 270 nm) by
E(eff) in uW/cm(2) (136,150).
To protect HCWs who are exposed to germicidal UV radiation for 8
hours per workday, the measured irradiance (E) should be less
than or equal to 0.2 uW/cm(2). This is calculated by obtaining If
(0.1 uW/cm(2)) (Table S3-3) and then dividing this value by S
lambda (0.5).
E. Maintenance and Monitoring
1. Labelling and posting
Warning signs should be posted on UV lamps and wherever
high-intensity (i.e., UV exposure greater than the REL)
germicidal UV irradiation is present (e.g., upper-room air
space and accesses to ducts [if duct irradiation is used]) to
alert maintenance staff or other HCWs of the hazard. Some
examples are shown below:
(For Table S3-3, see printed copy)
______________________ ______________________
| | | |
| CAUTION | | CAUTION |
| ULTRAVIOLET ENERGY: | | |
|TURN OFF LAMPS BEFORE | | ULTRAVIOLET ENERGY: |
| ENTERING UPPER ROOM | | PROTECT EYES & SKIN |
|______________________| |______________________|
2. Maintenance
Because the intensity of UV lamps fluctuates as they age, a
schedule for replacing the lamps should be developed. The
schedule can be determined from either a time/use log or a
system based on cumulative time. The tube should be checked
periodically for dust build-up, which lessens the output of
UVGI. If the tube is dirty, it should be allowed to cool, then
cleaned with a damp cloth. Tubes should be replaced if they
stop glowing or if they flicker to an objectionable extent.
Maintenance personnel must turn off all UV tubes before
entering the upper part of the room or before accessing ducts
for any purpose. Only a few seconds of direct exposure to the
intense UV radiation in the upper-room air space or in ducts
can cause burns. Protective equipment (e.g., gloves and
goggles [and/or face shields]) should be worn if exposure
greater than the recommended standard is anticipated.
Banks of UVGI tubes can be installed in ventilating ducts.
Safety devices should be used on access doors to eliminate
hazard to maintenance personnel. For duct irradiation systems,
the access door for servicing the lamps should have an
inspection window* through which the lamps are checked
periodically for dust build-up and malfunctioning. The access
door should have a warning sign written in languages appropriate
for maintenance personnel to alert them to the health hazard
of looking directly at bare tubes. The lock for this door should
have an automatic electric switch or other device that turns
off the lamps when the door is opened.
__________
* Ordinary glass (not quartz) is sufficient to filter out UV radiation.
Two types of fixtures are used in upper-room air irradiation:
wall-mounted fixtures that have louvers to block downward
radiation and ceiling-mounted fixtures that have baffles to
block radiation below the horizontal plane of the UV tube. The
actual UV tube in either type of fixture must not be visible
from any normal position in the room. Light switches that can
be locked should be used, if possible, to prevent injury to
personnel who might unintentionally turn the lamps on during
maintenance procedures.
In most applications, properly shielding the UV lamps to
provide protection from most, if not all, of the direct UV
radiation is not difficult. However, radiation reflected from
glass, polished metal, and high-gloss ceramic paints can be
harmful to persons in the room, particularly if more than one
UV lamp is in use. Surfaces in irradiated rooms that can
reflect UVGI into occupied areas of the room should be covered
with non-UV reflecting material.
3. Monitoring
A regularly scheduled evaluation of the UV intensity to which
HCWs, patients, and others are exposed should be conducted.
UV measurements should be made in various locations within a
room using a detector designed to be most sensitive at 254 nm.
Equipment used to measure germicidal UV radiation should be
maintained and calibrated on a regular schedule.
A new UV installation must be carefully checked for hot spots
(i.e., areas of the room where the REL is exceeded) by an
industrial hygienist or other person knowledgeable in making UV
measurements. UV radiation levels should not exceed those in
the recommended guidelines.
Supplement 4: Respiratory Protection
I. Considerations for Selection of Respirators
Personal respiratory protection should be used by a) persons entering
rooms where patients with known or suspected infectious TB are being
isolated, b) persons present during cough-inducing or aerosol-generating
procedures performed on such patients, and c) persons in other settings
where administrative and engineering controls are not likely to protect
them from inhaling infectious airborne droplet nuclei. These other
settings should be identified on the basis of the facility's risk
assessment.
Although data regarding the effectiveness of respiratory protection
from many hazardous airborne materials have been collected, the precise
level of effectiveness in protecting HCWs from M. tuberculosis
transmission in health-care settings has not been determined.
Information concerning the transmission of M. tuberculosis is
incomplete. Neither the smallest infectious dose of M. tuberculosis nor
the highest level of exposure to M. tuberculosis at which transmission
will not occur has been defined conclusively (59,151,152). Furthermore,
the size distribution of droplet nuclei and the number of particles
containing viable M. tuberculosis that are expelled by infectious TB
patients have not been defined adequately, and accurate methods of
measuring the concentration of infectious droplet nuclei in a room have
not been developed.
Nevertheless, in certain settings the administrative and engineering
controls may not adequately protect HCWs from airborne droplet nuclei
(e.g., in TB isolation rooms, treatment rooms in which cough-inducing or
aerosol-generating procedures are performed, and ambulances during
the transport of infectious TB patients). Respiratory protective devices
used in these settings should have characteristics that are suitable for
the organism they are protecting against and the settings in which they
are used.
A. Performance Criteria for Personal Respirators for Protection
Against Transmission of M. tuberculosis
Respiratory protective devices used in health-care settings for
protection against M. tuberculosis should meet the following
standard criteria. These criteria are based on currently available
information, including a) data on the effectiveness of respiratory
protection against noninfectious hazardous materials in
workplaces other than health-care settings and on an
interpretation of how these data can be applied to respiratory
protection against M. tuberculosis; b) data on the efficiency of
respirator filters in filtering biological aerosols; c) data on
face-seal leakage; and d) data on the characteristics of
respirators that were used in conjunction with administrative and
engineering controls in outbreak settings where transmission to
HCWs and patients was terminated.
1. The ability to filter particles 1 um in size in the unloaded
state with a filter efficiency of greater than or equal to 95%
(i.e., filter leakage of less than or equal to 5%), given flow
rates of up to 50 L per minute.
Available data suggest that infectious droplet nuclei range
in size from 1 um to 5 um; therefore, respirators used in
health-care settings should be able to efficiently filter the
smallest particles in this range. Fifty liters per minute is a
reasonable estimate of the highest airflow rate an HCW is
likely to achieve during breathing, even while performing
strenuous work activities.
2. The ability to be qualitatively or quantitatively fit
tested in a reliable way to obtain a face-seal leakage of less
than or equal to 10% (54,55).
3. The ability to fit the different facial sizes and
characteristics of HCWs, which can usually be met by making the
respirators available in at least three sizes.
4. The ability to be checked for facepiece fit, in accordance
with OSHA standards and good industrial hygiene practice, by
HCWs each time they put on their respirators (54,55).
In some settings, HCWs may be at risk for two types of exposure:
a) inhalation of M. tuberculosis and b) mucous membrane exposure
to fluids that may contain bloodborne pathogens. In these settings,
protection against both types of exposure should be used.
When operative procedures (or other procedures requiring a sterile
field) are performed on patients who may have infectious TB,
respiratory protection worn by the HCW should serve two functions:
a) it should protect the surgical field from the respiratory
secretions of the HCW and b) it should protect the HCW from
infectious droplet nuclei that may be expelled by the patient or
generated by the procedure. Respirators with expiration valves and
positive-pressure respirators do not protect the sterile field;
therefore, a respirator that does not have a valve and that meets
the criteria in Supplement 4, Section I.A, should be used.
B. Specific Respirators
The OSHA respiratory protection standard requires that all
respiratory protective devices used in the workplace be certified
by NIOSH.* NIOSH-approved HEPA respirators are the only currently
available air-purifying respirators that meet or exceed the standard
performance criteria stated above. However, the NIOSH certification
procedures are currently being revised (153). Under the proposed
revision, filter materials would be tested at a flow rate of 85
L/min for penetration by particles with a median aerodynamic
diameter of 0.3 um and, if certified, would be placed in one of the
following categories: type A, which has greater than or equal to
99.97% efficiency (similar to current HEPA filter media); type B,
greater than or equal to 99% efficiency; or type C, greater than
or equal to 95% efficiency. According to this proposed scheme,
type C filter material would meet or exceed the standard performance
criteria specified in this document.
__________
* 29 CFR Part 1910.134.
The facility's risk assessment may identify a limited number of
selected settings (e.g., bronchoscopy performed on patients
suspected of having TB or autopsy performed on deceased persons
suspected of having had active TB at the time of death) where the
estimated risk for transmission of M. tuberculosis may be such
that a level of respiratory protection exceeding the standard
criteria is appropriate. In such circumstances, a level of
respiratory protection exceeding the standard criteria and
compatible with patient-care delivery (e.g., negative-pressure
respirators that are more protective; powered air-purifying
particulate respirators [PAPRs]; or positive-pressure airline,
half-mask respirators) should be provided by employers to HCWs
who are exposed to M. tuberculosis. Information on these and other
respirators may be found in the NIOSH Guide to Industrial
Respiratory Protection (55).
C. The Effectiveness of Respiratory Protective Devices
The following information, which is based on experience with
respiratory protection in the industrial setting, summarizes the
available data about the effectiveness of respiratory protection
against hazardous airborne materials. Data regarding protection
against transmission of M. tuberculosis are not available.
The parameters used to determine the effectiveness of a
respiratory protective device are face-seal efficacy and filter
efficacy.
1. Face-seal leakage
Face-seal leakage compromises the ability of particulate
respirators to protect HCWs from airborne materials (154-156).
A proper seal between the respirator's sealing surface and the
face of the person wearing the respirator is essential for
effective and reliable performance of any negative-pressure
respirator. This seal is less critical, but still important, for
positive-pressure respirators. Face-seal leakage can result from
various factors, including incorrect facepiece size or shape,
incorrect or defective facepiece sealing-lip, beard growth,
perspiration or facial oils that can cause facepiece slippage,
failure to use all the head straps, incorrect positioning of
the facepiece on the face, incorrect head strap tension or
position, improper respirator maintenance, and respirator damage.
Every time a person wearing a negative-pressure particulate
respirator inhales, a negative pressure (relative to the
workplace air) is created inside the facepiece. Because of
this negative pressure, air containing contaminants can take
a path of least resistance into the respirator -- through leaks
at the face-seal interface -- thus avoiding the higher-resistance
filter material. Currently available, cup-shaped, disposable
particulate respirators have from 0 to 20% face-seal leakage
(55,154). This face-seal leakage results from the variability of
the human face and from limitations in the respirator's design,
construction, and number of sizes available. The face-seal
leakage is probably higher if the respirator is not fitted
properly to the HCW's face, tested for an adequate fit by a
qualified person, and then checked for fit by the HCW every time
the respirator is put on. Face-seal leakage may be reduced to
less than 10% with improvements in design, a greater variety
in available sizes, and appropriate fit testing and fit checking.
In comparison with negative-pressure respirators,
positive-pressure respirators produce a positive pressure
inside the facepiece under most conditions of use. For example,
in a PAPR, a blower forcibly draws ambient air through HEPA
filters, then delivers the filtered air to the facepiece. This
air is blown into the facepiece at flow rates that generally
exceed the expected inhalation flow rates. The positive
pressure inside the facepiece reduces face-seal leakage to low
levels, particularly during the relatively low inhalation
rates expected in health-care settings. PAPRs with a
tight-fitting facepiece have less than 2% face-seal leakage
under routine conditions (55). Powered-air respirators with
loose-fitting facepieces, hoods, or helmets have less than 4%
face-seal leakage under routine conditions (55). Thus, a PAPR
may offer lower levels of face-seal leakage than nonpowered,
half-mask respirators. Full facepiece, nonpowered respirators
have the same leakage (i.e., less than 2%) as PAPRs.
Another factor contributing to face-seal leakage of
cup-shaped, disposable respirators is that some of these
respirators are available in only one size. A single size may
produce higher leakage for persons who have smaller or
difficult-to-fit faces (157). The facepieces used for some
reusable (including HEPA and replaceable filter,
negative-pressure) and all positive-pressure particulate
air-purifying respirators are available in as many as three
different sizes.
2. Filter leakage
Aerosol leakage through respirator filters depends on at least
five independent variables: a) the filtration characteristics
for each type of filter, b) the size distribution of the
droplets in the aerosol, c) the linear velocity through the
filtering material, d) the filter loading (i.e., the amount of
contaminant deposited on the filter), and e) any electrostatic
charges on the filter and on the droplets in the aerosol (158).
When HEPA filters are used in particulate air-purifying
respirators, filter efficiency is so high (i.e., effectively
100%) that filter leakage is not a consideration. Therefore, for
all HEPA-filter respirators, virtually all inward leakage of
droplet nuclei occurs at the respirator's face seal.
3. Fit testing
Fit testing is part of the respiratory protection program
required by OSHA for all respiratory protective devices used
in the workplace. A fit test determines whether a respiratory
protective device adequately fits a particular HCW. The HCW
may need to be fit tested with several devices to determine
which device offers the best fit. However, fit tests can
detect only the leakage that occurs at the time of the fit
testing, and the tests cannot distinguish face-seal leakage
from filter leakage.
Determination of facepiece fit can involve qualitative or
quantitative tests (55). A qualitative test relies on the
subjective response of the HCW being fit tested. A
quantitative test uses detectors to measure inward leakage.
Disposable, negative-pressure particulate respirators can be
qualitatively fit tested with aerosolized substances that can
be tasted, although the results of this testing are limited
because the tests depend on the subjective response of the HCW
being tested. Quantitative fit testing of disposable
negative-pressure particulate respirators can best be performed
if the manufacturer provides a test respirator with a probe for
this purpose.
Replaceable filter, negative-pressure particulate respirators
and all positive-pressure particulate respirators can be fit
tested reliably, both qualitatively and quantitatively, when
fitted with HEPA filters.
4. Fit checking
A fit check is a maneuver that an HCW performs before each use
of the respiratory protective device to check the fit. The fit
check can be performed according to the manufacturer's
facepiece fitting instructions by using the applicable
negative-pressure or positive-pressure test.
Some currently available cup-shaped, disposable
negative-pressure particulate respirators cannot be fit checked
reliably by persons wearing the devices because occluding the
entire surface of the filter is difficult. Strategies for
overcoming these limitations are being developed by respirator
manufacturers.
5. Reuse of respirators
Conscientious respirator maintenance should be an integral
part of an overall respirator program. This maintenance
applies both to respirators with replaceable filters and
respirators that are classified as disposable but that are
reused. Manufacturers' instructions for inspecting, cleaning,
and maintaining respirators should be followed to ensure that
the respirator continues to function properly (55).
When respirators are used for protection against noninfectious
aerosols (e.g., wood dust), which may be present in the air in
heavy concentrations, the filter material may become occluded
with airborne material. This occlusion may result in an
uncomfortable breathing resistance. In health-care settings
where respirators are used for protection against biological
aerosols, the concentration of infectious particles in the air
is probably low; thus, the filter material in a respirator is
very unlikely to become occluded with airborne material. In
addition, there is no evidence that particles impacting on the
filter material in a respirator are re-aerosolized easily. For
these reasons, the filter material used in respirators in the
health-care setting should remain functional for weeks to months.
Respirators with replaceable filters are reusable, and a
respirator classified as disposable may be reused by the same
HCW as long as it remains functional.
Before each use, the outside of the filter material should be
inspected. If the filter material is physically damaged or
soiled, the filter should be changed (in the case of respirators
with replaceable filters) or the respirator discarded (in the
case of disposable respirators). Infection-control personnel
should develop standard operating procedures for storing,
reusing, and disposing of respirators that have been designated
as disposable and for disposing of replaceable filter elements.
II. Implementing a Personal Respiratory Protection Program
If personal respiratory protection is used in a health-care setting,
OSHA requires that an effective personal respiratory protection
program be developed, implemented, administered, and periodically
reevaluated (54,55).
All HCWs who need to use respirators for protection against infection
with M. tuberculosis should be included in the respiratory protection
program. Visitors to TB patients should be given respirators to wear
while in isolation rooms, and they should be given general
instructions on how to use their respirators.
The number of HCWs included in the respiratory protection program in
each facility will vary depending on a) the number of potentially
infectious TB patients, b) the number of rooms or areas to which
patients with suspected or confirmed infectious TB are admitted, and c)
the number of HCWs needed in these rooms or areas. Where respiratory
protection programs are required, they should include enough HCWs to
provide adequate care for a patient with known or suspected TB should
such a patient be admitted to the facility. However, administrative
measures should be used to limit the number of HCWs who need to enter
these rooms or areas, thus limiting the number of HCWs who need to be
included in the respiratory protection program.
Information regarding the development and management of a respiratory
protection program is available in technical training courses that
cover the basics of personal respiratory protection. Such courses are
offered by various organizations, such as NIOSH, OSHA, and the American
Industrial Hygiene Association. Similar courses are available from
private contractors and universities.
To be effective and reliable, respiratory protection programs must
contain at least the following elements (55,154):
1. Assignment of responsibility. Supervisory responsibility for the
respiratory protection program should be assigned to designated
persons who have expertise in issues relevant to the program,
including infectious diseases and occupational health.
2. Standard operating procedures. Written standard operating
procedures should contain information concerning all aspects of the
respiratory protection program.
3. Medical screening. HCWs should not be assigned a task requiring
use of respirators unless they are physically able to perform the
task while wearing the respirator. HCWs should be screened for
pertinent medical conditions at the time they are hired, then
rescreened periodically (55). The screening could occur as
infrequently as every 5 years. The screening process should begin
with a general screening (e.g., a questionnaire) for pertinent
medical conditions, and the results of the screening should then
be used to identify HCWs who need further evaluation. Routine
physical examination or testing with chest radiographs or
spirometry is not necessary or required.
Few medical conditions preclude the use of most negative-pressure
particulate respirators. HCWs who have mild pulmonary or cardiac
conditions may report discomfort with breathing when wearing
negative-pressure particulate respirators, but these respirators
are unlikely to have adverse health effects on the HCWs. Those HCWs
who have more severe cardiac or pulmonary conditions may have more
difficulty than HCWs with similar but milder conditions if
performing duties while wearing negative-pressure respirators.
Furthermore, these HCWs may be unable to use some PAPRs because of
the added weight of these respirators.
4. Training. HCWs who wear respirators and the persons who
supervise them should be informed about the necessity for wearing
respirators and the potential risks associated with not doing so.
This training should also include at a minimum:
* The nature, extent, and specific hazards of M. tuberculosis
transmission in their respective health-care facility.
* A description of specific risks for TB infection among persons
exposed to M. tuberculosis, of any subsequent treatment with
INH or other chemoprophylactic agents, and of the possibility
of active TB disease.
* A description of engineering controls and work practices and the
reasons why they do not eliminate the need for personal
respiratory protection.
* An explanation for selecting a particular type of respirator,
how the respirator is properly maintained and stored, and the
operation, capabilities, and limitations of the respirator
provided.
* Instruction in how the HCW wearing the respirator should inspect,
put on, fit check, and correctly wear the provided respirator
(i.e., achieve and maintain proper face-seal fit on the HCW's
face).
* An opportunity to handle the provided respirator and learn how to
put it on, wear it properly, and check the important parts.
* Instruction in how to recognize an inadequately functioning
respirator.
5. Face-seal fit testing and fit checking. HCWs should undergo fit
testing to identify a respirator that adequately fits each individual
HCW. The HCW should receive fitting instructions that include
demonstrations and practice in how the respirator should be worn,
how it should be adjusted, and how to determine if it fits
properly. The HCW should be taught to check the facepiece fit
before each use.
6. Respirator inspection, cleaning, maintenance, and storage.
Conscientious respirator maintenance should be an integral part of
an overall respirator program. This maintenance applies both to
respirators with replaceable filters and respirators that are
classified as disposable but that are reused. Manufacturers'
instructions for inspecting, cleaning, and maintaining respirators
should be followed to ensure that the respirator continues to
function properly (55).
7. Periodic evaluation of the personal respiratory protection
program. The program should be evaluated completely at least once
a year, and both the written operating procedures and program
administration should be revised as necessary based on the results
of the evaluation. Elements of the program that should be
evaluated include work practices and employee acceptance of
respirator use (i.e., subjective comments made by employees
concerning comfort during use and interference with duties).
Supplement 5: Decontamination -- Cleaning,
Disinfecting, and Sterilizing of Patient-Care Equipment
Equipment used on patients who have TB is usually not involved in the
transmission of M. tuberculosis, although transmission by contaminated
bronchoscopes has been demonstrated (159,160). Guidelines for cleaning,
disinfecting, and sterilizing equipment have been published (161,162). The
rationale for cleaning, disinfecting, or sterilizing patient-care
equipment can be understood more readily if medical devices, equipment,
and surgical materials are divided into three general categories. These
categories -- critical, semicritical, and noncritical items -- are defined
by the potential risk for infection associated with their use (163,164).
Critical items are instruments that are introduced directly into the
bloodstream or into other normally sterile areas of the body (e.g.,
needles, surgical instruments, cardiac catheters, and implants). These
items should be sterile at the time of use.
Semicritical items are those that may come in contact with mucous
membranes but do not ordinarily penetrate body surfaces (e.g., noninvasive
flexible and rigid fiberoptic endoscopes or bronchoscopes, endotracheal
tubes, and anesthesia breathing circuits). Although sterilization is
preferred for these instruments, high-level disinfection that destroys
vegetative microorganisms, most fungal spores, tubercle bacilli, and small
nonlipid viruses may be used. Meticulous physical cleaning of such items
before sterilization or high-level disinfection is essential.
Noncritical items are those that either do not ordinarily touch the
patient or touch only the patient's intact skin (e.g., crutches,
bedboards, blood pressure cuffs, and various other medical accessories).
These items are not associated with direct transmission of M.
tuberculosis, and washing them with detergent is usually sufficient.
Health-care facility policies should specify whether cleaning,
disinfecting, or sterilizing an item is necessary to decrease the risk for
infection. Decisions about decontamination processes should be based on
the intended use of the item, not on the diagnosis of the patient for whom
the item was used. Selection of chemical disinfectants depends on the
intended use, the level of disinfection required, and the structure and
material of the item to be disinfected.
Although microorganisms are ordinarily found on walls, floors, and other
environmental surfaces, these surfaces are rarely associated with
transmission of infections to patients or HCWs. This is particularly true
with organisms such as M. tuberculosis, which generally require inhalation
by the host for infection to occur. Therefore, extraordinary attempts to
disinfect or sterilize environmental surfaces are not indicated. If a
detergent germicide is used for routine cleaning, a hospital-grade,
EPA-approved germicide/disinfectant that is not tuberculocidal can be
used. The same routine daily cleaning procedures used in other rooms in
the facility should be used to clean TB isolation rooms, and personnel
should follow isolation practices while cleaning these rooms. For final
cleaning of the isolation room after a patient has been discharged,
personal protective equipment is not necessary if the room has been
ventilated for the appropriate amount of time (Table S3-1).
References
1. CDC. National action plan to combat multidrug-resistant tuberculosis.
Atlanta: US Department of Health and Human Services, Public Health
Service, CDC, 1992.
2. CDC. Guidelines for preventing the transmission of tuberculosis in
health-care settings, with special focus on HIV-related issues. MMWR
1990;39(No. RR-17).
3. CDC. Draft guidelines for preventing the transmission of tuberculosis
in health-care facilities, second edition; notice of comment period.
Federal Register 1993;58:52810-54.
4. CDC. Guidelines for prevention of TB transmission in hospitals.
Atlanta: US Department of Health and Human Services, Public Health
Service, CDC, 1982; DHHS publication no. (CDC)82-8371.
5. CDC. Screening for tuberculosis and tuberculous infection in high-risk
populations, and the use of preventive therapy for tuberculous
infection in the United States: recommendations of the Advisory
Committee for Elimination of Tuberculosis. MMWR 1990;39(No. RR-8).
6. American Thoracic Society/CDC. Diagnostic standards and classification
of tuberculosis. Am Rev Respir Dis 1990;142:725-35.
7. Wells WF. Aerodynamics of droplet nuclei. In: Airborne contagion and
air hygiene. Cambridge: Harvard University Press, 1955:13-9.
8. Selwyn PA, Hartel D, Lewis VA, et al. A prospective study of the risk
of tuberculosis among intravenous drug users with human
immunodeficiency virus infection. N Engl J Med 1989;320:545-50.
9. Di Perri G, Cruciani M, Danzi MC, et al. Nosocomial epidemic of active
tuberculosis among HIV-infected patients. Lancet 1989;2:1502-4.
10. Daley CL, Small PM, Schecter GF, et al. An outbreak of tuberculosis
with accelerated progression among persons infected with the human
immunodeficiency virus: an analysis using restriction-fragment-length
polymorphisms. N Engl J Med 1992;326:231-5.
11. Edlin BR, Tokars JI, Grieco MH, et al. An outbreak of
multidrug-resistant tuberculosis among hospitalized patients with the
acquired immunodeficiency syndrome. N Engl J Med 1992;326:1514-21.
12. Dooley SW, Villarino E, Lawrence M, et al. Nosocomial transmission of
tuberculosis in a hospital unit for HIV-infected patients. JAMA 1992;
267:2632-4.
13. Ten Dam HG. Research on BCG vaccination. Adv Tuberc Res
1984;21:79-106.
14. Barrett-Connor E. The epidemiology of tuberculosis in physicians.
JAMA 1979;241:33-8.
15. Brennen C, Muder RR, Muraca PW. Occult endemic tuberculosis in a
chronic care facility. Infect Control Hosp Epidemiol 1988;9:548-52.
16. Goldman KP. Tuberculosis in hospital doctors. Tubercle 1988;69:237-40.
17. Catanzaro A. Nosocomial tuberculosis. Am Rev Respir Dis
1982;125:559-62.
18. Ehrenkranz NJ, Kicklighter JL. Tuberculosis outbreak in a general
hospital: evidence of airborne spread of infection. Ann Intern Med
1972; 77:377-82.
19. Haley CE, McDonald RC, Rossi L, et al. Tuberculosis epidemic among
hospital personnel. Infect Control Hosp Epidemiol 1989;10:204-10.
20. Hutton MD, Stead WW, Cauthen GM, et al. Nosocomial transmission of
tuberculosis associated with a draining tuberculous abscess. J Infect
Dis 1990;161:286-95.
21. Kantor HS, Poblete R, Pusateri SL. Nosocomial transmission of
tuberculosis from unsuspected disease. Am J Med 1988;84:833-8.
22. Lundgren R, Norrman E, Asberg I. Tuberculous infection transmitted at
autopsy. Tubercle 1987;68:147-50.
23. CDC. Mycobacterium tuberculosis transmission in a health clinic --
Florida, 1988. MMWR 1989;38:256-8,263-4.
24. Beck-Sague C, Dooley SW, Hutton MD, et al. Outbreak of
multidrug-resistant Mycobacterium tuberculosis infections in a hospital:
transmission to patients with HIV infection and staff. JAMA
1992;268:1280-6.
25. CDC. Nosocomial transmission of multidrug-resistant tuberculosis to
health-care workers and HIV-infected patients in an urban hospital --
Florida. MMWR 1990;39:718-22.
26. CDC. Nosocomial transmission of multidrug-resistant tuberculosis among
HIV-infected persons -- Florida and New York, 1988-1991. MMWR 1991;
40:585-91.
27. Pearson ML, Jereb JA, Frieden TR, et al. Nosocomial transmission of
multidrug-resistant Mycobacterium tuberculosis: a risk to patients and
health care workers. Ann Intern Med 1992;117:191-6.
28. Dooley SW, Jarvis WR, Martone WJ, Snider DE Jr. Multidrug-resistant
tuberculosis [Editorial]. Ann Intern Med 1992;117:257-8.
29. Wenger P, Beck-Sague C, Otten J, et al. Efficacy of control measures
in preventing nosocomial transmission of multidrug-resistant
tuberculosis among patient and health-care workers [Abstract 53A]. In:
Program and abstracts of the World Congress on Tuberculosis. Bethesda,
MD: National Institutes of Health, Fogarty International Center, 1992.
30. Otten J, Chen J, Cleary T. Successful control of an outbreak of
multi-drug-resistant tuberculosis in an urban teaching hospital
[Abstract 51D]. In: Program and abstracts of the World Congress on
Tuberculosis. Bethesda, MD: National Institutes of Health, Fogarty
International Center, 1992.
31. Maloney S, Pearson M, Gordon M, et al. The efficacy of recommended
infection control measures in preventing nosocomial transmission of
multidrug-resistant TB [Abstract 51C]. In: Program and abstracts of
the World Congress on Tuberculosis. Bethesda, MD: National Institutes
of Health, Fogarty International Center, 1992.
32. Stroud L, Tokars J, Grieco M, Gilligan M, Jarvis W. Interruption of
nosocomial transmission of multidrug-resistant Mycobacterium
tuberculosis (MDR-TB) among AIDS patients in a New York City Hospital
[Abstract A1-3]. In: Third Annual Meeting of the Society for Hospital
Epidemiologists of America. Chicago: Society for Hospital
Epidemiologists of America, 1993.
33. American Thoracic Society. Treatment of tuberculosis and tuberculosis
infection in adults and children. Am J Respir Crit Care Med 1994;149:
1359-74.
34. Strong BE, Kubica GP. Isolation and identification of Mycobacterium
tuberculosis. Atlanta: US Department of Health and Human Services,
Public Health Service, CDC, 1981; DHHS publication no. (CDC)81-8390.
35. CDC. Tuberculosis and human immunodeficiency virus infection:
recommendations of the Advisory Committee for the Elimination of
Tuberculosis (ACET). MMWR 1989;38:236-8,243-50.
36. Willcox PA, Benator SR, Potgieter PD. Use of flexible fiberoptic
bronchoscope in diagnosis of sputum-negative pulmonary tuberculosis.
Thorax 1982;37:598-601.
37. Willcox PA, Potgieter PD, Bateman ED, Benator SR. Rapid diagnosis of
sputum-negative miliary tuberculosis using the flexible fiberoptic
bronchoscope. Thorax 1986;41:681-4.
38. Tenover FC, Crawford JT, Huebner RE, Geiter LJ, Horsburgh CR Jr, Good
RC. The resurgence of tuberculosis: is your laboratory ready? J Clin
Microbiol 1993;31:767-70.
39. Pitchenik AE, Cole C, Russell BW, et al. Tuberculosis, atypical
mycobacteriosis, and the acquired immunodeficiency syndrome among
Haitian and non-Haitian patients in South Florida. Ann Intern Med
1984;101:641-5.
40. Maayan S, Wormser GP, Hewlett D, et al. Acquired immunodeficiency
syndrome (AIDS) in an economically disadvantaged population. Arch
Intern Med 1985;145:1607-12.
41. Klein NC, Duncanson FP, Lenox TH III, et al. Use of mycobacterial
smears in the diagnosis of pulmonary tuberculosis in AIDS/ARC
patients. Chest 1989;95:1190-2.
42. Burnens AP, Vurma-Rapp U. Mixed mycobacterial cultures -- occurrence
in the clinical laboratory. Int J Med Microbiol 1989;27:85-90.
43. CDC. Initial therapy for tuberculosis in the era of multidrug
resistance: recommendations of the Advisory Council for the
Elimination of Tuberculosis. MMWR 1993;42(No. RR-7).
44. Rabalais G, Adams G, Stover B. PPD skin test conversion in health-care
workers after exposure to Mycobacterium tuberculosis infection in
infants [Letter]. Lancet 1991;338:826.
45. Wallgren A. On contagiousness of childhood tuberculosis. Acta Pediatr
Scand 1937;22:229-34.
46. Riley RL. Airborne infection. Am J Med 1974;57:466-75.
47. American Society of Heating, Refrigerating and Air-Conditioning
Engineers. Chapter 7: Health facilities. In: 1991 Application
handbook. Atlanta: American Society of Heating, Refrigerating and
Air-Conditioning Engineers, Inc., 1991.
48. American Institute of Architects, Committee on Architecture for
Health. Chapter 7: General hospital. In: Guidelines for construction
and equipment of hospital and medical facilities. Washington, DC: The
American Institute of Architects Press, 1987.
49. Health Resources and Services Administration. Guidelines for
construction and equipment of hospital and medical facilities.
Rockville, MD: US Department of Health and Human Services, Public
Health Service, 1984; PHS publication no. (HRSA)84-14500.
50. Riley RL, O'Grady F. Airborne infection: transmission and control. New
York: McMillan, 1961.
51. Galson E, Goddard KR. Hospital air conditioning and sepsis control.
ASHRAE Journal, 1968;(Jul):33-41.
52. Kethley TW. Air: its importance and control. In: Proceedings of the
National Conference on Institutionally Acquired Infections.
Washington, DC: US Department of Health, Education, and Welfare,
Public Health Service, Communicable Disease Center, Division of
Hospital and Medical Facilities, 1963:35-46; PHS publication no. 1188.
53. Hermans RD, Streifel AJ. Ventilation design. In: Bierbaum PJ, Lippmann
M, eds. Proceedings of the Workshop on Engineering Controls for
Preventing Airborne Infections in Workers in Health Care and Related
Facilities. Cincinnati: US Department of Health and Human Services,
Public Health Service, CDC, 1994; DHHS publication no. (NIOSH)94-106.
54. American National Standards Institute. American national standard
practices for respiratory protection. New York: American National
Standards Institute, 1992.
55. NIOSH. Guide to industrial respiratory protection. Morgantown, WV: US
Department of Health and Human Services, Public Health Service, CDC,
1987; DHHS publication no. (NIOSH)87-116.
56. CDC. Recommendations for HIV testing services for inpatients and
outpatients in acute-care hospital settings; and Technical guidance on
HIV counseling. MMWR 1993;42(No. RR-2).
57. Williams WW. Guidelines for infection control in hospital personnel.
Infect Control 1983;4(suppl):326-49.
58. Barrett-Connor E. The periodic chest roentgenogram for the control of
tuberculosis in health care personnel. Am Rev Respir Dis
1980;122:153-5.
59. CDC/National Institutes of Health. Agent: Mycobacterium tuberculosis,
M. bovis. In: Biosafety in microbiological and biomedical
laboratories. Atlanta: US Department of Health and Human Services,
Public Health Service, 1993:95; DHHS publication no. (CDC)93-8395.
60. CDC. Prevention and control of tuberculosis in facilities providing
long-term care to the elderly: recommendations of the Advisory
Committee for Elimination of Tuberculosis. MMWR 1990;39(No. RR-10).
61. CDC. Prevention and control of tuberculosis in correctional
institutions: recommendations of the Advisory Committee for the
Elimination of Tuberculosis. MMWR 1989;38:313-20,325.
62. Dueli RC, Madden RN. Droplet nuclei produced during dental treatment
of tubercular patients. Oral Surg 1970;30:711-6.
63. Manoff SB, Cauthen GM, Stoneburner RL, Bloch AB, Schultz S, Snider DE
Jr. TB patients with AIDS: are they more likely to spread TB?
[Abstract no. 4621]. Book 2. IV International Conference on AIDS.
Stockholm, Sweden, June 12-16, 1988:216.
64. Cauthen GM, Dooley SW, Bigler W, Burr J, Ihle W. Tuberculosis (TB)
transmission by HIV-associated TB cases [Abstract no. M.C.3326]. Vol
1. VII International Conference on AIDS. Florence, Italy, June 16-21,
1991.
65. Klausner JD, Ryder RW, Baende E, et al. Mycobacterium tuberculosis in
household contacts of human immunodeficiency virus type 1-seropositive
patients with active pulmonary tuberculosis in Kinshasa, Zaire. J
Infect Dis 1993;168:106-11.
66. Riley RL, Mills CC, O'Grady F, Sultan LU, Wittstadt F, Shivpuri DN.
Infectiousness of air from a tuberculosis ward. Am Rev Respir Dis
1962; 85:511-25.
67. Noble RC. Infectiousness of pulmonary tuberculosis after starting
chemotherapy: review of the available data on an unresolved question.
Am J Infect Control 1981;9:6-10.
68. Howard TP, Solomon DA. Reading the tuberculin skin test: who, when,
and how? Arch Intern Med 1988;148:2457-9.
69. Snider DE Jr. The tuberculin skin test. Am Rev Respir Dis
1982;125:108-18.
70. Huebner RE, Schein MF, Bass JB Jr. The tuberculin skin test. Clin
Infect Dis 1993;17:968-75.
71. Canessa PA, Fasano L, Lavecchia MA, Torraca A, Schiattone ML.
Tuberculin skin test in asymptomatic HIV seropositive carriers
[Letter]. Chest 1989;96:1215-6.
72. CDC. Purified protein derivative (PPD)-tuberculin anergy and HIV
infection: guidelines for anergy testing and management of anergic
persons at risk of tuberculosis. MMWR 1991;40(No. RR-5).
73. Snider DE, Farer LS. Package inserts for antituberculosis drugs and
tuberculins. Am Rev Respir Dis 1985;131:809-10.
74. Snider DE Jr. Bacille Calmette-Guerin vaccinations and tuberculin skin
test. JAMA 1985;253:3438-9.
75. CDC. Use of BCG vaccines in the control of TB: a joint statement by
the ACIP and the Advisory Committee for the Elimination of
Tuberculosis. MMWR 1988;37:663-4,669-75.
76. Thompson NJ, Glassroth JL, Snider DE Jr, Farer LS. The booster
phenomenon in serial tuberculin testing. Am Rev Respir Dis 1979;119:
587-97.
77. Des Prez RM, Heim CR. Mycobacterium tuberculosis. In: Mandell GL,
Douglas RG Jr, Bennett JE, eds. Principles and practice of infectious
diseases. 3rd ed. New York: Churchill Livingstone, 1990:1877-906.
78. Pitchenik AE, Rubinson HA. The radiographic appearance of tuberculosis
in patients with the acquired immune deficiency syndrome (AIDS) and
pre-AIDS. Am Rev Respir Dis 1985;131:393-6.
79. Kiehn TE, Cammarata R. Laboratory diagnosis of mycobacterial infection
in patients with acquired immunodeficiency syndrome. J Clin Microbiol
1986;24:708-11.
80. Crawford JT, Eisenach KD, Bates JH. Diagnosis of tuberculosis: present
and future. Semin Respir Infect 1989;4:171-81.
81. Moulding TS, Redeker AG, Kanel GC. Twenty isoniazid-associated deaths
in one state. Am Rev Respir Dis 1989;140:700-5.
82. Snider DE Jr, Layde PM, Johnson MW, Lyle MA. Treatment of tuberculosis
during pregnancy. Am Rev Respir Dis 1980;122:65-79.
83. Snider D. Pregnancy and tuberculosis. Chest 1984;86(suppl):10S-13S.
84. Hamadeh MA, Glassroth J. Tuberculosis and pregnancy. Chest 1992;101:
1114-20.
85. Glassroth JL, White MC, Snider DE Jr. An assessment of the possible
association of isoniazid with human cancer deaths. Am Rev Respir Dis
1977;116:1065-74.
86. Glassroth JL, Snider DE Jr, Comstock GW. Urinary tract cancer and
isoniazid. Am Rev Respir Dis 1977;116:331-3.
87. Costello HD, Snider DE Jr. The incidence of cancer among participants
in a controlled, randomized isoniazid preventive therapy trial. Am J
Epidemiol 1980;111:67-74.
88. CDC. The use of preventive therapy for tuberculous infection in the
United States: recommendations of the Advisory Committee for
Elimination of Tuberculosis. MMWR 1990;39 (No. RR-8):9-12.
89. CDC. Management of persons exposed to multidrug-resistant
tuberculosis. MMWR 1992;41(No. RR-11):59-71.
90. American Thoracic Society/CDC. Treatment of tuberculosis and
tuberculosis infection in adults and children, 1986. Am Rev Respir Dis
1986; 134:355-63.
91. American Thoracic Society/CDC. Control of tuberculosis in the United
States. Am Rev Respir Dis 1992;146:1624-35.
92. Snider DE Jr, Caras GJ. Isoniazid-associated hepatitis deaths: a
review of available information. Am Rev Respir Dis 1992;145:494-7.
93. Small PM, Shafer RW, Hopewell PC, et al. Exogenous infection with
multi-drug-resistant Mycobacterium tuberculosis in patients with
advanced HIV infection. N Engl J Med 1993;328:1137-44.
94. Iseman MD, Madsen LA. Drug-resistant tuberculosis. Clin Chest Med
1989; 10:341-53.
95. Goble M. Drug-resistant tuberculosis. Semin Respir Infect
1986;1:220-9.
96. Goble M, Iseman MD, Madsen LA, Waite D, Ackerson L, Horsburgh CR Jr.
Treatment of 171 patients with pulmonary tuberculosis resistant to
isoniazid and rifampin. N Engl J Med 1993;328:527-32.
97. Simone PM, Iseman MD. Drug-resistant tuberculosis: a deadly -- and
growing -- danger. J Respir Dis 1992;13:960-71.
98. American Conference of Governmental Industrial Hygienists. Industrial
ventilation: a manual of recommended practice. Cincinnati: American
Conference of Governmental Hygienists, Inc., 1992.
99. Mutchler JE. Principles of ventilation. In: NIOSH. The industrial
environment -- its evaluation and control. Washington, DC: US
Department of Health, Education, and Welfare, Public Health Service,
NIOSH, 1973.
100. Sherertz RJ, Belani A, Kramer BS, et al. Impact of air filtration on
nosocomial Aspergillus infections. Am J Med 1987;83:709-18.
101. Rhame FS, Streifel AJ, Kersey JH, McGlave PB. Extrinsic risk factors
for pneumonia in the patient at high risk of infection. Am J Med
1984;76: 42-52.
102. Opal SM, Asp AA, Cannady PB, Morse PL, Burton LJ, Hammer PG. Efficacy
of infection control measures during a nosocomial outbreak of
disseminated Aspergillus associated with hospital construction. J
Infect Dis 1986; 153:63-7.
103. Woods JE. Cost avoidance and productivity in owning and operating
buildings. Occup Med 1989;4:753-70.
104. Woods JE, Rask DR. Heating, ventilation, air-conditioning systems: the
engineering approach to methods of control. In: Kundsin RB, ed.
Architectural design and indoor microbial pollution. New York: Oxford
University Press, 1988:123-53.
105. American Society of Heating, Refrigerating and Air-Conditioning
Engineers. Chapter 25: Air cleaners for particulate contaminants. In:
1992 Systems and equipment fundamentals handbook. Atlanta: American
Society of Heating, Refrigerating and Air-Conditioning Engineers,
Inc., 1992:25.3-25.5.
106. American Society of Heating, Refrigerating and Air-Conditioning
Engineers. Chapter 14: Air flow around buildings. In: 1989
Fundamentals handbook. Atlanta: American Society of Heating,
Refrigerating and Air-Conditioning Engineers, Inc., 1989:14.1-14.13.
107. Riley RL, Wells WF, Mills CC, Nyka W, McLean RL. Air hygiene in
tuberculosis: quantitative studies of infectivity and control in a
pilot ward. Am Rev Tuberc 1957;75:420-31.
108. Riley RL, Nardell EA. Clearing the air: the theory and application of
UV air disinfection. Am Rev Respir Dis 1989;139:1286-94.
109. Riley RL. Ultraviolet air disinfection for control of respiratory
contagion. In: Kundsin RB, ed. Architectural design and indoor
microbial pollution. New York: Oxford University Press, 1988:175-97.
110. Stead WW. Clearing the air: the theory and application of ultraviolet
air disinfection [Letter]. Am Rev Respir Dis 1989;140:1832.
111. McLean RL. General discussion: the mechanism of spread of Asian
influenza. Am Rev Respir Dis 1961;83:36-8.
112. Willmon TL, Hollaender A, Langmuir AD. Studies of the control of acute
respiratory diseases among naval recruits. I. A review of a four-year
experience with ultraviolet irradiation and dust suppressive measures,
1943 to 1947. Am J Hyg 1948;48:227-32.
113. Wells WF, Wells MW, Wilder TS. The environmental control of epidemic
contagion. I. An epidemiologic study of radiant disinfection of air in
day schools. Am J Hyg 1942;35:97-121.
114. Wells WF, Holla WA. Ventilation in the flow of measles and chickenpox
through a community: progress report, January 1, 1946 to June 15, 1949
-- Airborne Infection Study, Westchester County Department of Health.
JAMA 1950;142:1337-44.
115. Perkins JE, Bahlke AM, Silverman HF. Effect of ultra-violet
irradiation of classrooms on spread of measles in large rural central
schools. Am J Public Health Nations Health 1947;37:529-37.
116. Lurie MB. Resistance to tuberculosis: experimental studies in native
and acquired defensive mechanisms. Cambridge, MA: Harvard University
Press, 1964:160-4.
117. Collins FM. Relative susceptibility of acid-fast and non-acid-fast
bacteria to ultraviolet light. Appl Microbiol 1971;21:411-3.
118. David HL, Jones WD Jr, Newman CM. Ultraviolet light inactivation and
photoreactivation in the mycobacteria. Infect Immun 1971;4:318-9.
119. David HL. Response of mycobacteria to ultraviolet light radiation. Am
Rev Respir Dis 1973;108:1175-85.
120. O. Riley RL, Knight M, Middlebrook G. Ultraviolet susceptibility of
BCG and virulent tubercle bacilli. Am Rev Respir Dis 1976;113:413-8.
121. American Thoracic Society/CDC. Control of tuberculosis. Am Rev Respir
Dis 1983;128:336-42.
122. National Tuberculosis and Respiratory Disease Association. Guidelines
for the general hospital in the admission and care of tuberculous
patients. Am Rev Respir Dis 1969;99:631-3.
123. CDC. Notes on air hygiene: summary of Conference on Air Disinfection.
Arch Environ Health 1971;22:473-4.
124. Schieffelbein CW Jr, Snider DE Jr. Tuberculosis control among homeless
populations. Arch Intern Med 1988;148:1843-6.
125. CDC. Prevention and control of tuberculosis in correctional
institutions: recommendations of the Advisory Committee for the
Elimination of Tuberculosis. MMWR 1989;38:313-20,325.
126. International Commission on Illumination. International lighting
vocabulary [French]. 4th ed. Geneva, Switzerland: Bureau Central de la
Commission Electrotechnique Internationale, 1987; CIE publication no.
17.4.
127. Nagy R. Application and measurement of ultraviolet radiation. Am Ind
Hyg Assoc J 1964;25:274-81.
128. Illuminating Engineering Society. IES lighting handbook. 4th ed. New
York: Illuminating Engineering Society, 1966:25-7.
129. Kethley TW, Branch K. Ultraviolet lamps for room air disinfection:
effect of sampling location and particle size of bacterial aerosol.
Arch Environ Health 1972;25:205-14.
130. Riley RL, Permutt S, Kaufman JE. Convection, air mixing, and
ultraviolet air disinfection in rooms. Arch Environ Health
1971;22:200-7.
131. Riley RL, Permutt S. Room air disinfection by ultraviolet irradiation
of upper air. Arch Environ Health 1971;22:208-19.
132. Riley RL, Permutt S, Kaufman JE. Room air disinfection by ultraviolet
irradiation of upper air: further analysis of convective air exchange.
Arch Environ Health 1971;23:35-9.
133. Riley RL, Kaufman JE. Air disinfection in corridors by upper air
irradiation with ultraviolet. Arch Environ Health 1971;22:551-3.
134. Mature JM, Alevantis LE, Chang Y-L, Liu K-S. Effect of ultraviolet
germicidal lamps on airborne microorganisms in an outpatient waiting
room. Applied Occupational and Environmental Hygiene 1992;7:505-13.
135. Riley RL, Kaufman JE. Effect of relative humidity on the inactivation
of airborne Serratia marcescens by ultraviolet radiation. Appl
Microbiol 1972;23:1113-20.
136. NIOSH. Criteria for a recommended standard...occupational exposure to
ultraviolet radiation. Washington, DC: US Department of Health,
Education, and Welfare, Public Health Service, 1972; publication no.
(HSM)73-110009.
137. Everett MA, Sayre RM, Olson RL. Physiologic response of human skin to
ultraviolet light. In: Urbach F, ed. The biologic effects of
ultraviolet radiation. Oxford, England: Pergamon Press, 1969.
138. International Agency for Research on Cancer. IARC monographs on the
evaluation of carcinogenic risks to humans: solar and ultraviolet
radiation. Vol 55. Lyon, France: World Health Organization,
International Agency for Research on Cancer, 1992.
139. Valerie K, Delers A, Bruck C, et al. Activation of human
immunodeficiency virus type 1 by DNA damage in human cells. Nature
1988;333:78-81.
140. Zmudzka BZ, Beer JZ. Activation of human immunodeficiency virus by
ultraviolet radiation (yearly review). Photochem Photobiol 1990;52:
1153-62.
141. Wallace BM, Lasker JS. Awakenings...UV light and HIV gene activation.
Science 1992;257:1211-2.
142. Valerie K, Rosenberg M. Chromatin structure implicated in activation
of HIV-1 gene expression by ultraviolet light. New Biol 1990;2:712-8.
143. Stein B, Rahmsdorf HJ, Steffen A, Litfin M, Herrlich P. UV-induced DNA
damage is an intermediate step in UV-induced expression of human
immunodeficiency virus type 1, collagenase, C-Fos, and
metallathionein. Mol Cell Biol 1989;9:5169-81.
144. Clerici M, Shearer GM. UV light exposure and HIV replication. Science
1992;258:1070-1.
145. NIOSH. Hazard evaluation and technical assistance report: Onondaga
County Medical Examiner's Office, Syracuse, New York. Cincinnati: US
Department of Health and Human Services, Public Health Service, CDC,
1992; NIOSH report no. HETA 92-171-2255.
146. NIOSH. Hazard evaluation and technical assistance report: John C.
Murphy Family Health Center, Berkeley, Missouri. Cincinnati: US
Department of Health and Human Services, Public Health Service, CDC,
1992; NIOSH report no. HETA 91-148-2236.
147. NIOSH. Hazard evaluation and technical assistance report: San
Francisco General Hospital and Medical Center, San Francisco,
California. Cincinnati: US Department of Health and Human Services,
Public Health Service, CDC, 1992; NIOSH report no. HETA 90-122-L2073.
148. Mature JM. Ultraviolet radiation and ventilation to help control
tuberculosis transmission: guidelines prepared for California Indoor
Air Quality Program. Berkeley, CA: Air and Industrial Hygiene
Laboratory, 1989.
149. Riley RL. Principles of UV air disinfection. Baltimore, MD: Johns
Hopkins University, School of Hygiene and Public Health, 1991.
150. American Conference of Governmental Industrial Hygienists. Threshold
limit values and biological exposure indices for 1991-1992.
Cincinnati: American Conference of Governmental Industrial Hygienists,
Inc., 1991.
151. Bloom BR, Murray CJL. Tuberculosis: commentary on a reemergent killer.
Science 1992;257:1055-64.
152. Nardell EA. Dodging droplet nuclei: reducing the probability of
nosocomial tuberculosis transmission in the AIDS era. Am Rev Respir
Dis 1990;142:501-3.
153. US Department of Health and Human Services. 42 CFR Part 84:
Respiratory protective devices; proposed rule. Federal Register
1994;59:26849-89.
154. American National Standards Institute. ANSI Z88.2-1980: American
national standard practices for respiratory protection. New York:
American National Standards Institute, 1980.
155. Hyatt EC. Current problems and new developments in respiratory
protection. Am Ind Hyg Assoc J 1963;24:295-304.
156. American National Standards Institute. ANSI Z88.2-1969: American
national standard practices for respiratory protection. New York:
American National Standards Institute, 1969.
157. Lowry PL, Hesch PR, Revoir WH. Performance of single-use respirators.
Am Ind Hyg Assoc J 1977;38:462-7.
158. Hyatt EC, et al. Respiratory studies for the National Institute for
Occupational Safety and Health -- July 1, 1972, through June 3, 1973.
Los Alamos, NM: Los Alamos Scientific Laboratory; progress report no.
LA-5620-PR.
159. Nelson KE, Larson PA, Schraufnagel DE, Jackson J. Transmission of
tuberculosis by fiber bronchoscopes. Am Rev Respir Dis
1983;127:97-100.
160. Leers WD. Disinfecting endoscopes: how not to transmit Mycobacterium
tuberculosis by bronchoscopy. Can Med Assoc J 1980;123:275-83.
161. Garner JS, Simmons BP. Guideline for isolation precautions in
hospitals. Infect Control 1983;4(suppl):245-325.
162. Rutala WA. APIC guidelines for selection and use of disinfectants. Am
J Infect Control 1990;18:99-117.
163. Favero MS, Bond WW. Chemical disinfection of medical and surgical
materials. In: Block SS, ed. Disinfection, sterilization, and
preservation. 4th ed. Philadelphia: Lea & Fabiger, 1991:617-41.
164. Garner JS, Favero MS. Guideline for handwashing and hospital
environmental control. Atlanta: US Department of Health and Human
Services, Public Health Service, CDC, 1985.
Glossary
This glossary contains many of the terms used in the guidelines, as well
as others that are encountered frequently by persons who implement TB
infection-control programs. The definitions given are not dictionary
definitions but are those most applicable to usage relating to TB.
Acid-fast bacilli (AFB): Bacteria that retain certain dyes after being
washed in an acid solution. Most acid-fast organisms are mycobacteria.
When AFB are seen on a stained smear of sputum or other clinical
specimen, a diagnosis of TB should be suspected; however, the
diagnosis of TB is not confirmed until a culture is grown and identified
as M. tuberculosis.
Adherence: Refers to the behavior of patients when they follow all
aspects of the treatment regimen as prescribed by the medical provider,
and also refers to the behavior of HCWs and employers when they follow all
guidelines pertaining to infection control.
Aerosol: The droplet nuclei that are expelled by an infectious person
(e.g., by coughing or sneezing); these droplet nuclei can remain
suspended in the air and can transmit M. tuberculosis to other persons.
AIA: The American Institute of Architects, a professional body that
develops standards for building ventilation.
Air changes: The ratio of the volume of air flowing through a space
in a certain period of time (i.e., the airflow rate) to the volume of that
space (i.e., the room volume); this ratio is usually expressed as the
number of air changes per hour (ACH).
Air mixing: The degree to which air supplied to a room mixes with the
air already in the room, usually expressed as a mixing factor. This factor
varies from 1 (for perfect mixing) to 10 (for poor mixing), and it is used
as a multiplier to determine the actual airflow required (i.e., the
recommended ACH multiplied by the mixing factor equals the actual ACH
required).
Alveoli: The small air sacs in the lungs that lie at the end of the
bronchial tree; the site where carbon dioxide in the blood is replaced
by oxygen from the lungs and where TB infection usually begins.
Anergy: The inability of a person to react to skin-test antigens (even
if the person is infected with the organisms tested) because of
immunosuppression.
Anteroom: A small room leading from a corridor into an isolation room;
this room can act as an airlock, preventing the escape of contaminants
from the isolation room into the corridor.
Area: A structural unit (e.g., a hospital ward or laboratory) or
functional unit (e.g., an internal medicine service) in which HCWs provide
services to and share air with a specific patient population or work with
clinical specimens that may contain viable M. tuberculosis organisms. The
risk for exposure to M. tuberculosis in a given area depends on the
prevalence of TB in the population served and the characteristics of the
environment.
ASHRAE: The American Society of Heating, Refrigerating and
Air-Conditioning Engineers, Inc., a professional body that develops
standards for building ventilation.
Asymptomatic: Without symptoms, or producing no symptoms.
Bacillus of Calmette and Guerin (BCG) vaccine: A TB vaccine used in
many parts of the world.
BACTEC(R): One of the most often used radiometric methods for detecting
the early growth of mycobacteria in culture. It provides rapid growth (in
7-14 days) and rapid drug-susceptibility testing (in 5-6 days). When
BACTEC(R) is used with rapid species identification methods, M.
tuberculosis can be identified within 10-14 days of specimen collection.
Booster phenomenon: A phenomenon in which some persons (especially older
adults) who are skin tested many years after infection with M.
tuberculosis have a negative reaction to an initial skin test, followed by
a positive reaction to a subsequent skin test. The second (i.e., positive)
reaction is caused by a boosted immune response. Two-step testing is used
to distinguish new infections from boosted reactions (see Two-step
testing).
Bronchoscopy: A procedure for examining the respiratory tract that
requires inserting an instrument (a bronchoscope) through the mouth or
nose and into the trachea. The procedure can be used to obtain diagnostic
specimens.
Capreomycin: An injectable, second-line anti-TB drug used primarily for
the treatment of drug-resistant TB.
Cavity: A hole in the lung resulting from the destruction of pulmonary
tissue by TB or other pulmonary infections or conditions. TB patients who
have cavities in their lungs are referred to as having cavitary disease,
and they are often more infectious than TB patients without cavitary
disease.
Chemotherapy: Treatment of an infection or disease by means of oral or
injectable drugs.
Cluster: Two or more PPD skin-test conversions occurring within a
3-month period among HCWs in a specific area or occupational group, and
epidemiologic evidence suggests occupational (nosocomial) transmission.
Contact: A person who has shared the same air with a person who has
infectious TB for a sufficient amount of time to allow possible
transmission of M. tubercuosis.
Conversion, PPD: See PPD test conversion.
Culture: The process of growing bacteria in the laboratory so that
organisms can be identified.
Cycloserine: A second-line, oral anti-TB drug used primarily for treating
drug-resistant TB.
Directly observed therapy (DOT): An adherence-enhancing strategy in
which an HCW or other designated person watches the patient swallow each
dose of medication.
DNA probe: A technique that allows rapid and precise identification of
mycobacteria (e.g., M. tuberculosis and M. bovis) that are grown in
culture. The identification can often be completed in 2 hours.
Droplet nuclei: Microscopic particles (i.e., 1-5 um in diameter)
produced when a person coughs, sneezes, shouts, or sings. The droplets
produced by an infectious TB patient can carry tubercle bacilli and can
remain suspended in the air for prolonged periods of time and be carried
on normal air currents in the room.
Drug resistance, acquired: A resistance to one or more anti-TB drugs
that develops while a patient is receiving therapy and which usually
results from the patient's nonadherence to therapy or the prescription of
an inadequate regimen by a health-care provider.
Drug resistance, primary: A resistance to one or more anti-TB drugs that
exists before a patient is treated with the drug(s). Primary resistance
occurs in persons exposed to and infected with a drug-resistant strain of
M. tuberculosis.
Drug-susceptibility pattern: The anti-TB drugs to which the tubercle
bacilli cultured from a TB patient are susceptible or resistant based on
drug-susceptibility tests.
Drug-susceptibility tests: Laboratory tests that determine whether the
tubercle bacilli cultured from a patient are susceptible or resistant to
various anti-TB drugs.
Ethambutol: A first-line, oral anti-TB drug sometimes used concomitantly
with INH, rifampin, and pyrazinamide.
Ethionamide: A second-line, oral anti-TB drug used primarily for treating
drug-resistant TB.
Exposure: The condition of being subjected to something (e.g.,
infectious agents) that could have a harmful effect. A person exposed to
M. tuberculosis does not necessarily become infected (see Transmission).
First-line drugs: The most often used anti-TB drugs (i.e., INH, rifampin,
pyrazinamide, ethambutol, and streptomycin).
Fixed room-air HEPA recirculation systems: Nonmobile devices or systems
that remove airborne contaminants by recirculating air through a HEPA
filter. These may be built into the room and permanently ducted or may be
mounted to the wall or ceiling within the room. In either situation, they
are fixed in place and are not easily movable.
Fluorochrome stain: A technique for staining a clinical specimen with
fluorescent dyes to perform a microscopic examination (smear) for
mycobacteria. This technique is preferable to other staining techniques
because the mycobacteria can be seen easily and the slides can be read
quickly.
Fomites: Linens, books, dishes, or other objects used or touched by a
patient. These objects are not involved in the transmission of M.
tuberculosis.
Gastric aspirate: A procedure sometimes used to obtain a specimen for
culture when a patient cannot cough up adequate sputum. A tube is inserted
through the mouth or nose and into the stomach to recover sputum that was
coughed into the throat and then swallowed. This procedure is particularly
useful for diagnosis in children, who are often unable to cough up sputum.
High-efficiency particulate air (HEPA) filter: A specialized filter that
is capable of removing 99.97% of particles greater than or equal to 0.3
um in diameter and that may assist in controlling the transmission of M.
tuberculosis. Filters may be used in ventilation systems to remove
particles from the air or in personal respirators to filter air before it
is inhaled by the person wearing the respirator. The use of HEPA filters
in ventilation systems requires expertise in installation and maintenance.
Human immunodeficiency virus (HIV) infection: Infection with the virus
that causes acquired immunodeficiency syndrome (AIDS). HIV infection is
the most important risk factor for the progression of latent TB infection
to active TB.
Immunosuppressed: A condition in which the immune system is not
functioning normally (e.g., severe cellular immunosuppression resulting
from HIV infection or immunosuppressive therapy). Immunosuppressed persons
are at greatly increased risk for developing active TB after they have
been infected with M. tuberculosis. No data are available regarding
whether these persons are also at increased risk for infection with M.
tuberculosis after they have been exposed to the organism.
Induration: An area of swelling produced by an immune response to an
antigen. In tuberculin skin testing or anergy testing, the diameter of the
indurated area is measured 48-72 hours after the injection, and the result
is recorded in millimeters.
Infection: The condition in which organisms capable of causing disease
(e.g., M. tuberculosis) enter the body and elicit a response from the
host' s immune defenses. TB infection may or may not lead to clinical
disease.
Infectious: Capable of transmitting infection. When persons who have
clinically active pulmonary or laryngeal TB disease cough or sneeze, they
can expel droplets containing M. tuberculosis into the air. Persons whose
sputum smears are positive for AFB are probably infectious.
Injectable: A medication that is usually administered by injection into
the muscle (intramuscular [IM]) or the bloodstream (intravenous [IV]).
Intermittent therapy: Therapy administered either two or three times per
week, rather than daily. Intermittent therapy should be administered only
under the direct supervision of an HCW or other designated person (see
Directly observed therapy [DOT]).
Intradermal: Within the layers of the skin.
Isoniazid (INH): A first-line, oral drug used either alone as preventive
therapy or in combination with several other drugs to treat TB disease.
Kanamycin: An injectable, second-line anti-TB drug used primarily for
treatment of drug-resistant TB.
Latent TB infection: Infection with M. tuberculosis, usually detected
by a positive PPD skin-test result, in a person who has no symptoms of
active TB and who is not infectious.
Mantoux test: A method of skin testing that is performed by injecting
0.1 mL of PPD-tuberculin containing 5 tuberculin units into the dermis
(i.e., the second layer of skin) of the forearm with a needle and syringe.
This test is the most reliable and standardized technique for tuberculin
testing (see Tuberculin skin test and Purified protein derivative
[PPD]-tuberculin test).
Multidrug-resistant tuberculosis (MDR-TB): Active TB caused by M.
tuberculosis organisms that are resistant to more than one anti-TB drug;
in practice, often refers to organisms that are resistant to both INH and
rifampin with or without resistance to other drugs (see Drug resistance,
acquired and Drug resistance, primary).
M. tuberculosis complex: A group of closely related mycobacterial species
that can cause active TB (e.g., M. tuberculosis, M. bovis, and M.
africanum); most TB in the United States is caused by M. tuberculosis.
Negative pressure: The relative air pressure difference between two areas
in a health-care facility. A room that is at negative pressure has a lower
pressure than adjacent areas, which keeps air from flowing out of the room
and into adjacent rooms or areas.
Nosocomial: An occurrence, usually an infection, that is acquired in a
hospital or as a result of medical care.
Para-aminosalicylic acid: A second-line, oral anti-TB drug used for
treating drug-resistant TB.
Pathogenesis: The pathologic, physiologic, or biochemical process by
which a disease develops.
Pathogenicity: The quality of producing or the ability to produce
pathologic changes or disease. Some nontuberculous mycobacteria are
pathogenic (e.g., Mycobacterium kansasii), and others are not (e.g.,
Mycobacterium phlei).
Portable room-air HEPA recirculation units: Free-standing portable
devices that remove airborne contaminants by recirculating air through a
HEPA filter.
Positive PPD reaction: A reaction to the purified protein derivative
(PPD)-tuberculin skin test that suggests the person tested is infected
with M. tuberculosis. The person interpreting the skin-test reaction
determines whether it is positive on the basis of the size of the
induration and the medical history and risk factors of the person being
tested.
Preventive therapy: Treatment of latent TB infection used to prevent the
progression of latent infection to clinically active disease.
Purified protein derivative (PPD)-tuberculin: A purified tuberculin
preparation that was developed in the 1930s and that was derived from old
tuberculin. The standard Mantoux test uses 0.1 mL of PPD standardized to 5
tuberculin units.
Purified protein derivative (PPD)-tuberculin test: A method used to
evaluate the likelihood that a person is infected with M. tuberculosis. A
small dose of tuberculin (PPD) is injected just beneath the surface of the
skin, and the area is examined 48-72 hours after the injection. A reaction
is measured according to the size of the induration. The classification of
a reaction as positive or negative depends on the patient's medical
history and various risk factors (see Mantoux test).
Purified protein derivative (PPD)-tuberculin test conversion: A
change in PPD test results from negative to positive. A conversion within
a 2-year period is usually interpreted as new M. tuberculosis infection,
which carries an increased risk for progression to active disease. A
booster reaction may be misinterpreted as a new infection (see Booster
phenomenon and Two-step testing).
Pyrazinamide: A first-line, oral anti-TB drug used in treatment regimens.
Radiography: A method of viewing the respiratory system by using
radiation to transmit an image of the respiratory system to film. A chest
radiograph is taken to view the respiratory system of a person who is
being evaluated for pulmonary TB. Abnormalities (e.g., lesions or
cavities in the lungs and enlarged lymph nodes) may indicate the presence
of TB.
Radiometric method: A method for culturing a specimen that allows for
rapid detection of bacterial growth by measuring production of CO(2) by
viable organisms; also a method of rapidly performing susceptibility
testing of M. tuberculosis.
Recirculation: Ventilation in which all or most of the air that is
exhausted from an area is returned to the same area or other areas of the
facility.
Regimen: Any particular TB treatment plan that specifies which drugs are
used, in what doses, according to what schedule, and for how long.
Registry: A record-keeping method for collecting clinical, laboratory, and
radiographic data concerning TB patients so that the data can be organized
and made available for epidemiologic study.
Resistance: The ability of some strains of bacteria, including M.
tuberculosis, to grow and multiply in the presence of certain drugs that
ordinarily kill them; such strains are referred to as drug-resistant
strains.
Rifampin: A first-line, oral anti-TB drug that, when used concomitantly
with INH and pyrazinamide, provides the basis for short-course therapy.
Room-air HEPA recirculation systems and units: Devices (either fixed or
portable) that remove airborne contaminants by recirculating air through a
HEPA filter.
Second-line drugs: Anti-TB drugs used when the first-line drugs
cannot be used (e.g., for drug-resistant TB or because of adverse
reactions to the first-line drugs). Examples are cycloserine,
ethionamide, and capreomycin.
Single-pass ventilation: Ventilation in which 100% of the air
supplied to an area is exhausted to the outside.
Smear (AFB smear): A laboratory technique for visualizing mycobacteria.
The specimen is smeared onto a slide and stained, then examined using a
microscope. Smear results should be available within 24 hours. In TB, a
large number of myco-bacteria seen on an AFB smear usually indicates
infectiousness. However, a positive result is not diagnostic of TB because
organisms other than M. tuberculosis may be seen on an AFB smear (e.g.,
nontuberculous mycobacteria).
Source case: A case of TB in an infectious person who has transmitted M.
tuberculosis to another person or persons.
Source control: Controlling a contaminant at the source of its generation,
which prevents the spread of the contaminant to the general work space.
Specimen: Any body fluid, secretion, or tissue sent to a laboratory where
smears and cultures for M. tuberculosis will be performed (e.g., sputum,
urine, spinal fluid, and material obtained at biopsy).
Sputum: Phlegm coughed up from deep within the lungs. If a patient has
pulmonary disease, an examination of the sputum by smear and culture can
be helpful in evaluating the organism responsible for the infection.
Sputum should not be confused with saliva or nasal secretions.
Sputum induction: A method used to obtain sputum from a patient who is
unable to cough up a specimen spontaneously. The patient inhales a saline
mist, which stimulates a cough from deep within the lungs.
Sputum smear, positive: AFB are visible on the sputum smear when viewed
under a microscope. Persons with a sputum smear positive for AFB are
considered more infectious than those with smear-negative sputum.
Streptomycin: A first-line, injectable anti-TB drug.
Symptomatic: Having symptoms that may indicate the presence of TB or
another disease (see Asymptomatic).
TB case: A particular episode of clinically active TB. This term
should be used only to refer to the disease itself, not the patient with
the disease. By law, cases of TB must be reported to the local health
department.
TB infection: A condition in which living tubercle bacilli are present
in the body but the disease is not clinically active. Infected persons
usually have positive tuberculin reactions, but they have no symptoms
related to the infection and are not infectious. However, infected persons
remain at lifelong risk for developing disease unless preventive therapy
is given.
Transmission: The spread of an infectious agent from one person to
another. The likelihood of transmission is directly related to the
duration and intensity of exposure to M. tuberculosis (see Exposure).
Treatment failures: TB disease in patients who do not respond to
chemotherapy and in patients whose disease worsens after having improved
initially.
Tubercle bacilli: M. tuberculosis organisms.
Tuberculin skin test: A method used to evaluate the likelihood that a
person is infected with M. tuberculosis. A small dose of PPD-tuberculin is
injected just beneath the surface of the skin, and the area is examined
48-72 hours after the injection. A reaction is measured according to the
size of the induration. The classification of a reaction as positive or
negative depends on the patient's medical history and various risk factors
(see Mantoux test, PPD test).
Tuberculosis (TB): A clinically active, symptomatic disease caused by
an organism in the M. tuberculosis complex (usually M. tuberculosis or,
rarely, M. bovis or M. africanum).
Two-step testing: A procedure used for the baseline testing of persons
who will periodically receive tuberculin skin tests (e.g., HCWs) to reduce
the likelihood of mistaking a boosted reaction for a new infection. If the
initial tuberculin-test result is classified as negative, a second test is
repeated 1-3 weeks later. If the reaction to the second test is positive,
it probably represents a boosted reaction. If the second test result is
also negative, the person is classified as not infected. A positive
reaction to a subsequent test would indicate new infection (i.e., a
skin-test conversion) in such a person.
Ultraviolet germicidal irradiation (UVGI): The use of ultraviolet
radiation to kill or inactivate microorganisms.
Ultraviolet germicidal irradiation (UVGI) lamps: Lamps that kill or
inactivate microorganisms by emitting ultraviolet germicidal radiation,
predominantly at a wavelength of 254 nm (intermediate light waves between
visible light and X-rays). UVGI lamps can be used in ceiling or wall
fixtures or within air ducts of ventilation systems.
Ventilation, dilution: An engineering control technique to dilute and
remove airborne contaminants by the flow of air into and out of an area.
Air that contains droplet nuclei is removed and replaced by
contaminant-free air. If the flow is sufficient, droplet nuclei become
dispersed, and their concentration in the air is diminished.
Ventilation, local exhaust: Ventilation used to capture and remove
airborne contaminants by enclosing the contaminant source (i.e., the
patient) or by placing an exhaust hood close to the contaminant source.
Virulence: The degree of pathogenicity of a microorganism as
indicated by the severity of the disease produced and its ability to
invade the tissues of a host. M. tuberculosis is a virulent organism.
INDEX
Acid-fact bacilli smears (see Smears, AFB)
Acquired immunodeficiency syndrome (see HIV
infection)
Administrative controls ........................................... 2, 3, 33
Aerosol therapy .......................................... 5, 33, 34, 69, 70
Aerosolized pentamidine
Booths for administration ........................................ 70, 71
Patient screening .................................................... 35
Risk for nosocomial transmission of M. tuberculosis ................... 5
Tents for administration ......................................... 70, 71
AFB smears (see Smears, AFB)
AIDS (see HIV infection)
Air changes per hour (ACH) .............................. 21, 29, 30, 84, 87
ASHRAE recommendations ....................................... 29, 51, 69
Determining .............................................. 29, 72, 74, 75
Removal efficiencies ............................................. 70, 72
Airflow
Monitoring direction .......................................... 69, 78-81
Ambulatory-care settings/areas
Management of patients .................................... 13, 20, 25-27
American Conference of Governmental Industrial
Hygienists, Inc. (ACGIH) ............................................. 69
American Institute of Architects (AIA) .......................... 29, 69, 87
American Society of Hearing, Refrigerating and
Air-Conditioning Engineers, Inc. (ASHRAE) ................ 29, 51, 69, 87
Americans With Disabilities Act of 1990 ................................. 38
Anergy testing .................................................. 37, 38, 62
Anesthesia considerations ........................................... 35, 50
Anterooms........................................................ 30, 50, 77
Negative pressure for ................................................ 77
Assignment of responsibility ................................ 8, 12, 20, 102
Autopsy
Risk for nosocomial transmission of M. Tuberculosis ........... 5, 33, 99
Autopsy rooms ................................................ 5, 33, 51, 99
HEPA filtration ...................................................... 51
Respiratory protection ........................................... 51, 99
UVGI ................................................................. 51
Bacteriology
Collecting specimens ............................................. 24, 64
Mixed mycobacterial infection ........................................ 64
BCG (Bacille of Calmette and Guerin) vaccine ..................... 5, 39, 90
Skin testing ..................................................... 39, 63
Vaccination ................................................... 5, 39, 63
Bronchoscopy .................................................... 34, 35, 64
Ventilation .......................................................... 35
Chest radiography (see Diagnosis of TB)
Cluster (see PPD testing) ................................... 10, 11, 16, 17
Cohorting ............................................................... 27
Community TB profile ............................................. 9, 12, 17
Confidentiality .................................. 3, 18, 36, 38, 40, 48, 49
Contact investigation ................................ 36, 42, 43, 47-50, 63
Correctional facilities ................................................. 52
Cough-inducing procedures .................................... 6, 14, 21, 58
Bronchoscopy ......................................................... 35
General guidelines ....................................... 19, 21, 34, 35
Home-health-care settings ............................................ 54
In ambulatory-care areas ............................................. 26
Patient recovery from ................................................ 35
Pentamidine, aerosolized .......................................... 6, 35
Respiratory protection ........................................ 33-35, 97
Risk for nosocomial transmission of M. tuberculosis ............... 7, 27
Sputum induction ...................................................... 6
Counseling ......................................... 6, 7, 14, 21, 37, 53-55
Immunocompromised workers ............................... 6, 7, 21, 53-55
Culture methods
Radiometric ...................................................... 24, 64
Decontamination of patient-care equipment .............................. 105
Supplement 5--Decontamination, disinfecting, and
sterilizing of patient-care equipment ............................ 105
Dental care ..................................................... 33, 52, 53
Dental settings
Infection-control precautions, TB ................................ 52, 53
PPD screening program ........................................ 16, 48, 50
Risk assessment ............................................... 8, 16, 52
Diagnosis TB ........................................ 12, 13, 24, 26, 27, 51
Anergy testing ........................................... 37, 38, 59, 62
Bacteriology (see Smears, AFB and Culture methods)
Before aerosol therapy ............................................... 35
Bronchoscopy ..................................................... 35, 64
Chest radiograph ......................................... 25, 28, 49, 50
Culturing ........................................................ 49, 50
DNA probes ............................................... 11, 18, 27, 48
Fluorescent microscopy ............................................... 24
High-pressure liquid chromatography .................................. 24
Hospitalized patients ............................................ 27, 28
Index of suspicion ............................................ 8, 24, 59
Mantoux technique .................................................... 59
Medical history .................................................. 12, 53
NAP test ............................................................. 24
Nucleic acid probes .............................................. 24, 64
PPD testing .......................................................... 25
Radiometric culture .............................................. 24, 25
Smears ....................................................... 24, 25, 64
Supplement 2 -- Diagnosis and treatment of latent TB
infection and active TB ........................................... 59
With anergy .......................................................... 25
With immunocompromising conditions ................................... 25
With simultaneous pulmonary infection ................................ 25
Directly observed therapy (DOT) ................................. 25, 53, 66
Home-health-care settings ........................................ 53, 66
Public health department ......................................... 25, 66
Discharge planning ........................................... 9, 13, 31, 49
Drug-resistant TB ..................... 2, 6, 11, 19, 27, 30, 37, 48, 57, 66
Drug-susceptibility testing .................................. 9, 24, 28, 66
On initial isolates .............................................. 28, 66
Radiometric methods .................................................. 24
Reporting to public health department ................................ 66
Education and training ................... 2, 14, 19, 21, 36, 51, 53, 55, 92
Emergency medical services ................................... 3, 33, 51, 52
PPD screening program ................................................ 52
Respiratory protection ........................................... 33, 51
Emergency departments ........................................ 3, 20, 25, 32
Management of patients ........................................... 13, 25
Endotracheal intubation ..................................... 5, 34, 52, 105
Engineering controls ................ 2, 3, 7, 12, 13, 20, 21, 29-33, 47, 69
Epidemiology, pathogenesis, and transmission of
M. tuberculosis .................................................... 4, 5
Executive summary ..................................................... 1, 2
General ventilation .................................. 20, 26, 29-31, 73, 69
Dilution and removal ....................................... 5, 7, 30, 73
Facility airflow direction .................................... 73, 76-81
Mixing factor ........................................................ 75
Negative pressure ......................................... 29, 76-81, 86
Recirculating systems ..................... 20, 29, 30, 32, 73, 82-84, 88
Room airflow patterns ............................................. 73-75
Short-circuiting ................................................. 74, 75
Single-pass systems .............................................. 20, 73
Glossary ............................................................... 113
Health-care facility, definition ......................................... 3
Health-care worker(s) (HCW[s])
Confidentiality ................................... 3, 18, 36, 38, 40, 48
Counseling ...................................... 6, 8, 14, 21, 37, 53-55
Risk for infection ................................................ 37
Risk for infection and disease in
immunocompromised HCWs ..................................... 37, 38
Job reassignment .................................................. 38
Definition ............................................................... 3
Education and training .................... 2, 14, 19, 21, 36, 51, 53-55, 92
Evaluating PPD conversions .............................................. 37
Evaluating positive PPD-test results ................................ 14, 37
Immunocompromised ................................................... 36, 37
Preventive therapy .............................................. 36, 37, 65
Screening for active TB ............................................. 14, 38
Screening for latent TB infection ................................... 14, 38
Training ................................................................ 36
Workplace restrictions .................................................. 41
Active TB ........................................................ 38, 41
Latent TB infection .................................................. 41
Health department ................................. 8, 21, 25, 31, 43, 47-50
Case notification ............................................ 25, 43, 48
Health Resources and Services Administration ........................ 29, 87
Heat wheel energy recovery units,
HEPA filtration for................................................... 82
Hierarchy of controls ...................................... 1, 6, 7, 36, 86
High-effeciency particulate (HEPA filtration ......................... 81-87
Autopsy rooms ........................................................ 51
Disposable prefilters to extend life ............................. 85, 86
DOP penetration test ................................................. 85
Efficiency ............................................... 32, 81, 85, 86
Enclosing booth use .................................. 32, 71, 73, 81, 82
In ambulatory-care areas ......................................... 26, 32
Individual room-air recirculation ......................... 32, 81-84, 86
Installation, maintenance, and monitoring .................... 32, 81, 85
Longevity ........................................................ 85, 86
Pressure-sensing device to determine replacement
need .............................................................. 85
Recirculation of HEPA-filtered air within a room .. 20, 21, 30, 59, 81-84
Evaluation .................................................... 69, 84
Fixed room-air recirculation systems ............... 29, 32, 81-84, 86
Portable room-air recirculation units ......... 29, 32, 81, 82, 84, 86
Recirculation of HEPA-filtered air to other areas of
facility .............................................. 30, 32, 81, 82
Use when exhausting air to the outside ............... 32, 73, 74, 81, 82
High-risk area ........................................ 9, 10, 12-15, 17, 22
HIV infection
Anergy testing
Cell-mediated immunity, impaired ............................. 25, 36, 37
Chest radiography .................................................... 25
Coinfection with M. tuberculosis ............................... 4, 5, 36
Counseling HIV-infected HCWs ...................................... 36-38
Evaluation of PPD skin-test results .......................... 25, 38, 61
Likelihood of infection after exposure to
M. tuberculosis .................................................... 5
Progression from latent TB infection to active TB ................... 4-6
Smears, AFB .......................................................... 25
Home-health-care settings ............................................ 3, 53
Cough-inducing procedures ............................................ 54
PPD screening program ................................................ 54
Respiratory protection ........................................... 53, 54
Hospices ............................................................. 3, 52
Human immunodeficiency virus (see HIV infection)
Infection control
Development of the TB infection-control plan .......................... 8
Engineering controls .........3, 7, 12, 20, 21, 31, 33, 47, 53, 55, 69-95
Evaluation of engineering controls ................................... 19
Fundamentals ................................................. 6-8, 12-15
Hierarchy of control measures ......................................... 6
Observation of infection-control practices ....................... 12, 19
Infection-control practices, evaluating effectiveness ................... 19
Infectiousness
Determining ...................................................... 57, 58
Factors determining ...................................... 27, 40, 41, 57
In HIV-infected patients ............................................. 57
Length of, on therapy ................................................ 57
Monitoring ........................................................... 58
Pediatric patients ............................................... 27, 57
Supplement 1--Determining the infectiousness of a
TB patient .....................................................57, 58
Noninfectiousness .................................................... 31
Intensive-care units .................................................... 27
Intermediate-risk area ....................................... 9, 16, 17, 22
Isolation practices
Dental settings .................................................. 52, 53
Discontinuation .......................................... 13, 27, 30, 31
Facilitating patient adherence ....................................... 28
For multidrug-resistant TB ........................................... 31
Initiation ....................................................... 13, 27
Intensive-care units ................................................. 27
Keeping door to room closed .................................. 28, 29, 79
Long-term-care facilities ............................................ 52
Minimizing access to room ............................................ 28
Patient education .................................................... 28
Pediatric patients ................................................... 27
Visitors ......................................................... 27, 28
Isolation rooms
Air changes per hour (ACH) ............................... 29, 72, 74, 87
Air exhaust ...................................................... 29, 87
Anteroom ............................................................. 30
Grouping ............................................................. 30
HEPA filtration .................................................. 30, 86
Keeping door to room closed ...................................... 29, 77
Negative pressure ................................................ 29, 87
Number required .................................................. 13, 30
Purpose .......................................................... 29, 86
Ultraviolet germicidal irradiation (UVGI) ........................ 30, 86
Isoniazid (INH)
During pregnancy ..................................................... 65
Hepatitis ............................................................ 65
Monitoring for adverse reactions ..................................... 66
Preventive therapy regimen ........................................... 65
Laboratories ......................................... 3, 12, 23, 24, 51, 59
Local exhaust ventilation ............................. 7, 20, 21, 35, 69-73
Discharge from booths, tents, and hoods ...................... 70, 71, 73
Exterior devices ................................................. 70, 71
Into TB isolation rooms .......................................... 71, 73
Long-term-care facilities ............................................... 52
Low-risk areas ........................................... 9, 10, 16, 22, 23
Medical offices .................................................. 3, 54, 55
Medical record review .................................... 9, 18, 19, 24, 49
Minimal-risk facility ............................................. 9-11, 23
Mycobacterium avium complex ......................................... 25, 64
National Institute for Occupational Safety and
Health (NIOSH) ................................... 34, 91-93, 98, 99, 102
Negative pressure
Alternate methods for achieving .................................. 77, 78
Definition ........................................................... 76
Monitoring .................................................... 29, 78-80
Pressure differential required ....................................76, 77
Pressure-sensing devices............................................79-81
Pressurizing the corridor ............................................ 78
Smoke-tube testing ................................... 74, 75, 78, 79, 81
TB isolation rooms ........................................... 29, 80, 81
Tents and booths ................................................. 71, 73
Nosocomial transmission ............................ 3, 5, 11, 16-18, 21, 47
Factors promoting .............................................. 5, 6, 23
Occupational groups .......................................... 10, 11, 16-19
Occupational Safety and Health Administration (OSHA) ...33, 34, 98, 100, 102
Operating rooms ......................................................... 50
Anterooms ............................................................ 50
Respiratory protection ........................................... 50, 51
Ventilation ...................................................... 35, 50
OSHA respiratory protection standard ...................... 34, 98, 100, 102
Outbreaks of TB in health-care facilities ..................... 2, 6, 50, 97
Patient-to-patient transmission
Cohorting ............................................................ 27
Investigating ........................................................ 48
Pediatric patients .............................................. 27, 57, 68
Pneumocystis carinii ................................................ 25, 36
PPD reading
Cut-points for risk groups .................................... 60-63, 65
PPD testing ............................................................. 53
Analysis of increased conversion rate ........................ 11, 12, 18
Anergy ................................................... 37, 38, 54, 61
BCG vaccination .......................................... 37, 39, 54, 63
Booster phenomenon ............................................... 55, 63
Cluster ...................................................... 10, 11, 17
Contact investigation ...................... 8, 25, 36, 42, 43, 47-50, 61
Conversions ............... 8, 11, 16-23, 36, 37, 39-45, 47-49, 60-63, 65
Dental settings ...................................................... 53
Emergency medical services ....................................... 51, 52
Evaluating PPD conversion ..................... 8, 18, 20, 21, 36, 39, 47
Frequency ................................. 18, 21, 38-40, 43, 49, 52, 54
HCWs with positive PPD test ............................... 12, 14, 39-41
Home-health-care settings .................................... 14, 53, 54
Immunocompromised workers ....................... 4-6, 21, 26, 31, 37, 38
Interpretation of results ......................................... 60-64
Mantoux technique .................................................... 59
Occupational group ....................................... 10, 11, 17, 40
Persons with HIV infection ........................ 25, 38, 39, 60-62, 65
Positive-predictive value .................................... 60, 61, 63
Pregnancy ............................................................ 61
Recent PPD converters ..................................... 40, 60-63, 65
Recording results ............................................ 17, 18, 40
Self-reading results ................................................. 59
Staggered testing .................................................... 39
Two-step testing ................................................. 39, 63
Preventive therapy .................................................. 65, 66
Drug-susceptibility testing ...................................... 40, 42
For anergic persons .................................................. 65
Monitoring ........................................................... 66
Pregnancy ............................................................ 65
Regimens ............................................................. 65
Problem evaluation ............................................... 14, 41-49
Active TB in HCWs ..................................... 14, 40-42, 47, 48
Contact investigation ......................................... 43, 48-50
Patient-to-patient transmission .............................. 14, 48, 49
PPD test conversions in HCWs .................................. 42-45, 47
Public health department
Contact investigation .................................... 15, 25, 49, 50
Coordination ............................................. 21, 25, 49, 50
Directly observed therapy (DOT) .............................. 25, 31, 66
Discharge planning ....................................... 13, 25, 31, 66
Providing assistance ..................................... 31, 43, 47, 50
Reporting ................................................ 15, 25, 48, 50
Radiographs ............... 4, 5, 24, 35, 40, 42, 49, 57, 59-60, 62, 64, 103
Radiology department ............................................ 28, 32, 49
Re-entrainment ...................................................... 87, 88
Recommendations
Aerosolized pentamidine .......................................... 35, 70
AFB smears ........................................... 24, 30, 41, 58, 64
Analysis of PPD screening data ................................... 11, 17
Anergy testing ....................................................... 62
Anterooms .................................................... 30, 50, 77
Autopsy rooms ........................................................ 51
Bronchoscopy ....................................... 35, 64, 76, 99, 105
Case surveillance .................................................... 17
Community TB profile ...................................... 9. 11, 12, 17
Contact investigation ..................................... 15, 43, 47-50
Correctional facilities ........................................... 3, 52
Cough-inducing procedures ........7, 11, 14, 19, 21, 27, 33-35, 52, 54-58
........................................................... 76, 82, 97
Development of the TB infection-control plan .............. 6, 19, 51, 69
Diagnosis ..................... 30, 35, 37, 38, 40, 41, 49, 53, 55, 59-65
Discharge planning .................................... 8, 13, 25, 31, 66
Drug-susceptibility testing ............... 24, 25, 27 40, 42, 50, 58, 66
Emergency departments .............................. 3, 9, 20, 25, 31, 32
Emergency medical services .................................... 3, 51, 52
Engineering controls .................................... 7, 31-33, 69-95
Environmental/engineering evaluation ...................... 9, 19, 20, 69
HCW counseling .............................. 6, 8, 14, 16, 21, 37, 53-55
HCW screening ........... 6, 8, 14, 17, 21, 37-39, 42, 43, 47, 51-54, 103
HEPA filtration .............. 30, 32, 69, 71, 73, 75, 81-87, 91, 98, 100
Home-health-care settings ..................................... 3, 53, 54
Hospices .......................................................... 3, 52
Identification of patients who may have active TB ................ 23, 24
Immunocompromised persons ......................... 6, 21, 26, 31, 37, 38
Infectiousness ................................... 27, 41, 53, 54, 57, 58
Initiation of TB isolation .......................... 5-7, 9, 13, 20, 27
Initiation of treatment .................... 5, 6, 17, 20, 23, 25, 40, 66
Isolation practices ...................................... 13, 27-29, 105
Correctional facilities ........................................... 52
Dental settings ............................................... 52, 53
Discontinuation of .................................... 27, 30, 53, 58
Laboratories ............................................. 13, 19, 24, 51
Long-term-care facilities ............................................ 52
Managing hospitalized patients ................................... 13, 20
Managing patients
In ambulatory-care settings ....................... 13, 20, 25, 26, 55
In correctional facilities .................................... 20, 52
In dental settings ............................................ 20, 52
In emergency departments .............................. 13, 20, 25, 26
In emergency medical services settings .................... 13, 20, 51
In home-health-care settings .................................. 20, 53
In hospices ................................................... 20, 53
In medical offices ........................................ 20, 54, 55
Mantoux technique .................................................... 59
Medical offices .................................................. 54, 55
Multidrug-resistant tuberculosis (MRD-TB) ............ 25, 26, 31, 37, 65
Observation of infection-control practices ................... 12, 19, 20
Operating rooms .................................................. 35, 50
Patient transport ........................................ 28, 33, 51, 97
Periodic reassessment .................................... 11, 12, 19, 20
Preventive therapy for TB infection ....................... 36-41, 65, 66
Problem evaluation ........................................ 14, 40-49, 51
Radiology department ..................................... 13, 15, 28, 49
Radiometric culture .............................................. 24, 25
Review of TB patient medical records ........... 9, 12, 17-20, 43, 47, 49
Risk assessment .. 7, 8-12, 16-20, 22, 23, 30, 38, 39, 51, 52, 54, 92, 99
Training ................. 6, 8, 21, 36, 37, 51, 54, 55, 59, 92, 102, 103
Treatment for active TB .9, 12, 17, 20, 23, 24, 30, 31, 35, 41, 59, 66-68
Treatment for latent TB ................................. 41, 65, 66, 103
Triage ................................................ 7, 11, 13, 16, 25
UVGI ............................... 7, 26, 30, 32, 33, 51, 69, 84, 88-92
UVGI maintenance .................................................. 92-95
Ventilation ................... 5-7, 20, 21, 26, 28-32, 35, 51, 54, 69-90
Waiting areas .......................... 5, 20, 26-28, 31, 32, 35, 53, 89
Work place restrictions .............................................. 41
Respiratory protection ........... 3, 6, 7, 13, 21, 28, 33-35, 50-55, 97-103
Cleaning ....................................................... 104, 105
Cough-inducing procedures ................. 14, 19, 21, 33-35, 54, 55, 97
Dental settings .................................................. 52, 53
Effectiveness .................................................... 97-102
Emergency medical services ........................................... 51
Face-seal leakage ............................................ 33, 97-101
Filter leakage ......................................... 33, 97, 100, 101
Fit checking ......................................... 100, 101, 103, 104
Fit testing ....................................... 33, 98, 100, 101, 104
Home-health-care settings ........................................ 53, 54
Maintenance ....................................... 34, 99, 101, 103, 104
Medical screening ................................................... 103
Negative-pressure respirators .......................... 33, 99, 100, 103
NIOSH ............................................ 34, 91-93, 98, 99, 102
Operating rooms .................................................. 35, 50
OSHA respiratory protection standard ............... 33, 34, 98, 100, 102
Performance criteria .................................. 21, 33, 51, 97-99
Positive-pressure respirators ............................ 34, 50, 98-100
Respiratory protection programs ............. 7, 13, 21, 34, 100, 102-104
Reuse of respirators ...................................... 101, 102, 104
Storage ........................................................ 103, 104
Supplement 4--Respiratory protection ............................ 97- 104
Surgery ..................................................... 33, 34, 105
Surgical masks for patients ............................... 26-28, 34, 53
Training ................................ 8, 21, 36, 51, 54, 55, 102, 103
Visitors of TB patients ................................. 27, 28, 34, 102
Respiratory protection program .................................. 13, 97-104
Elements ........................................................ 102-104
Periodic evaluation ................................................. 104
Risk assessment ....................................................... 7-22
Case surveillance ................................................ 12, 17
Community TB profile .......................................... 9, 11, 17
Elements of a risk assessment ..................................... 9, 11
Examples ......................................................... 22, 23
How to perform ................................................... 10, 11
Levels of risk ............................................. 9, 11, 12-17
Periodic reassessment ........................................ 12, 19, 22
Review of TB patient medical records ....................... 9, 12, 17-20
Risk area definitions ........................................ 11, 16, 17
Who should conduct ................................................. 3, 9
Risk factors for disease progression ...................... 4, 5, 37, 38, 60
Risk groups ......................................................... 60, 62
Signs and symptoms of active TB ......................... 20, 24, 36, 41, 49
Skin testing (see PPD testing)
smears, AFB ................... 5, 9, 18, 24, 25, 27, 30, 41, 50, 57, 58, 64
Smoke-tube testing .................................................. 74, 75
Smoke tubes .................................................. 74, 75, 78-81
Source control ............................................... 7, 69, 70, 71
Sputum induction ......................................... 5, 23, 35, 57, 70
Surgical masks
For patient transport ........................................ 28, 34, 51
For patients in ambulatory-care areas
or emergency departments ................................. 26, 34, 53-55
Visitors of TB patients .............................................. 27
TB infection-control program ................ 3, 6-8, 11, 19, 20, 36, 50, 69
Assigning supervisory responsibility ............................... 7, 8
Elements of a TB infection-control program ..................... 8, 11-19
TB isolation room ............................. 8, 13, 17, 29, 30, 50, 86-88
Achieving negative pressure .................................. 29, 76, 77
Anterooms .................................................... 30, 50, 77
Cohorting ............................................................ 27
Exhaust .............................................. 21, 29, 82, 83, 86
Grouping ......................................................... 30, 69
HEPA filtration .......................................... 29, 81, 84, 86
In ambulatory-case areas ............................................. 26
Negative pressure ..................................... 21, 29, 76-80, 87
Purpose .............................................................. 86
Ventilation .............. 21, 26, 27, 29, 31, 32, 69, 73, 76, 81, 86, 87
TB patient scheduling ............................................... 26, 28
Tissues ................................................................. 35
For hospitalized patients ............................................ 28
For patients in ambulatory-case areas
or emergency departments ........................................ 20, 26
Home-health-care settings ............................................ 53
Transporting TB patients .................................... 28, 33, 51, 97
Treatment for TB
Adherence ........................................................ 30, 36
Directly observed therapy (DOT) .................................. 25, 66
Dosage recommendations for children and adults .................... 66-68
Drug susceptibility .............................................. 17, 67
For active TB ..................................... 17, 40, 42, 66, 67
For latent TB infection ................................... 40, 42, 66
During pregnancy ..................................................... 65
For active TB ................................................. 66, 67
For latent TB infection ........................................... 65
Initiation of ................................................ 20, 23, 25
Preventive therapy ........................................... 41, 65, 66
Regimen options for children and adults .............................. 67
Supplement 2--Diagnosis and treatment for
latent TB infection and active TB ................................ 59-68
Treatment for active TB ........................... 12, 20, 24, 25, 66-68
Triage ................................................... 7, 11, 16, 25, 47
Tuberculin skin test (see PPD testing)
Ultraviolet germicidal irradiation (UVGI) .......... 7, 26, 30-32, 69, 88-95
Activation of HIV gene promoters ..................................... 91
Applications ................................................. 32, 89, 90
Autopsy rooms ........................................................ 51
Carcinogenicity ...................................................... 91
Definition ........................................................... 89
Determining maximum permissible exposure times ................... 92, 93
Duct irradiation ............................................. 32, 89, 94
Educating HCWs ....................................................... 92
Effectiveness ..................................................... 88-91
Exposure criteria for UV radiation ............................... 92, 93
HCW training issues .................................................. 92
In ambulatory-care settings .......................................... 89
Installation ................................................. 32, 33, 92
Labelling and posting caution signs .............................. 93, 94
Limitations ...................................................... 90, 91
Maintenance .......................................... 32, 33, 91, 94, 95
Monitoring ........................................................... 95
Obtaining consultation before installation ........................... 92
Precautions ....................................................... 91-94
Recommended exposure limits (RELs) ................................ 91-93
Safety issues ........................................................ 91
Upper-room air irradiation ........................... 30, 32, 89, 90, 94
UV radiation, definition ............................................. 89
Ventilation
Air changes per hour (ACH) ....... 21, 29, 30, 51, 70, 72, 75, 84, 87, 90
Airflow patterns .......................... 69, 73-75, 78, 79, 85, 89, 90
Ambulatory-care areas ................................................ 26
Anterooms .................................................... 30, 50, 77
Autopsy rooms ........................................................ 51
Correction facilities ................................................ 52
Dilution and removal .......................................... 69, 72-74
Direction of airflow ............................... 7, 32, 69, 73, 76-81
Discharge from booths, tents, and hoods .......... 32, 70, 71, 73, 81, 91
Emergency department ................................................. 32
Emergency medical services ....................................... 51, 52
Enclosing devices ........................................ 31, 69, 75, 77
Engineers ................................................ 31, 69, 75, 77
Evaluation ............................................ 9, 19, 31, 69, 85
Exhaust ............. 7, 20, 21, 29, 30, 32, 35, 51, 69-78, 81-84, 88, 91
General ventilation ............ 7, 20, 26, 29-32, 69, 73, 74, 76, 78, 81
................................................... 82, 84, 85, 87, 89
HEPA filter installation, maintenance, and monitoring .... 32, 81, 85, 86
Home-health-care settings ........................................ 53, 54
Hospices ............................................................. 52
Local exhaust ventilation ............................. 7, 21, 35, 69, 70
Discharge exhaust ............................................. 71, 73
Enclosing devices ............................................. 70, 71
Exterior devices .................................................. 71
Maintenance .................................. 13, 19, 21, 30, 69, 85, 86
Monitoring ................................................ 21, 29, 78-81
Mixing factor .................................................... 72, 75
Negative pressure ..................... 21, 29, 51, 69, 76, 77-82, 86, 87
Operating rooms .............................................. 35, 50, 51
Periodic evaluation .................................................. 69
Positive-pressure rooms .............................................. 35
Pressure-sensing devices ...................................... 79-81, 85
Pressurizing the corridor in induce negative pressure ................ 78
Radiology department ............................................. 28, 32
Rates (see Air changes per hour [ACH])
Recirculation of HEPA filtered air ................... 32, 51, 78, 82, 83
Fixed ......................................................... 83, 84
Portable ...................................................... 84, 85
Re-entrainment ................................................... 87, 88
Short-circuiting ............................................. 71, 74, 75
Single-pass system ................................................... 73
Source control methods ..................................... 7, 69, 70-73
Stagnation ........................................................ 74-76
Supplement 3--Engineering issues in TB control .................... 69-95
TB isolation rooms ......... 13, 21, 26-29, 31, 32, 69, 73, 76, 81, 86-88
Tents and booths (see Local exhaust ventilation)
Treatment rooms ................... 29, 30, 69, 73, 76, 80-82, 86, 87, 89
Ventilation rates .................................... 29, 74, 84, 87, 90
Waiting-rooms areas .................................. 26, 31, 32, 53, 55
Very low-risk area or facility ....................... 9, 11, 16, 30, 61, 62
Visitors ................................................................. 2
Contact investigation ............................................ 48, 57
Pediatric patients ................................................... 27
Protection against UVGI .............................................. 33
Respiratory protection for .............................. 28, 31, 34, 102
Waiting-room areas ....................... 5, 20, 26, 31, 32, 53, 55, 89, 90
Workplace reassignment .............................................. 37, 38
Workplace restrictions .............................................. 40, 41
Active TB ............................................................ 41
Extrapulmonary TB .................................................... 41
Latent TB infection .................................................. 40
Nonadherence to preventive therapy ................................... 41
Nonadherence to treatment ............................................ 41
Return to work ................................................... 40, 41
List of Tables
Table 1. Elements of a risk assessment of tuberculosis (TB)
in health-care facilities ............................................. 9
Table 2. Elements of a tuberculosis (TB) infection-control program ..... 12
Table 3. Characteristics of an effective tuberculosis (TB)
infection-control program ............................................ 20
Table 4. Examples of potential problems that can occur when identifying
or isolating patients who may have infectious tuberculosis (TB)....... 46
Table S2-1. Summary of interpretation of purified protein derivative
(PPD)-tuberculin skin-test results ................................... 62
Table S2-2. Regimen options for the treatment of tuberculosis (TB)
in children and adults ............................................... 67
Table S2-3. Dosage recommendations for the initial treatment
of tuberculosis in children and adults ............................... 68
Table S3-1. Air changes per hour (ACH) and time in minutes required
for removal efficiencies of 90%, 99%, and 99.9% of airborne
contaminants ......................................................... 72
Table S3-2. Hierarchy of ventilation methods for tuberculosis (TB)
isolation rooms and treatment rooms .................................. 86
Table S3-3. Maximum permissible exposure times for selected values of
effective irradiance ................................................. 93
List of Figures
Figure 1. Protocol for conducting a tuberculosis (TB) risk assessment in
a health-care facility ............................................... 10
Figure 2. Protocol for investigating purified protein derivative
(PPD)-tuberculin skin-test conversions in health-care workers (HCWs) .... 44
Figure S3-1. An enclosing booth designed to sweep air past a patient
who has active tuberculosis and entrap the infectious droplet nuclei
in a high-efficiency particulate air (HEPA) filter ................... 71
Figure S3-2. Room airflow patterns designed to provide mixing of air and
prevent passage of air directly from the air supply to the exhaust ... 75
Figure S3-3. Smoke-tube testing and anemometer placement to determine
the direction of airflow into and out of a room ...................... 79
Figure S3-4. Cross-sectional view of a room showing the location
of negative pressure measurement ..................................... 80
Figure S3-5. Fixed, ducted room-air recirculation system using a
high-efficiency particulate air (HEPA) filter inside an air duct ..... 83
Figure S3-6. Fixed ceiling-mounted room-air recirculation system using
a High-effeciency particulate air (HEPA) filter ...................... 83
Figure S3-7. Air recirculation zone created by wind blowing over a
building ............................................................. 88
Appendix B
Smoke-Trail Testing Method for Negative pressure Isolation Room
Test Method Description:
One of the purposes of a negative pressure TB isolation room is to prevent
TB droplet nuclei from escaping the isolation room and entering the
corridor or other surrounding uncontaminated spaces. To check for negative
room pressure, use smoke-trails to demonstrate that the pressure
differential is inducing airflow from the corridor, through the crack at
the bottom of the door (undercut) and into the isolation room. When
performing a smoke-trail test follow these recommendations where
applicable:
1. Test only with the isolation room door shut. If not equipped with an
anteroom, it is assumed that there will be a loss of space pressure
control when the isolation door is opened and closed. It is not
necessary to demonstrate direction of airflow when the door is open.
2. If there is an anteroom, release smoke at the inner door undercut, with
both anteroom doors shut.
3. In addition to a pedestrian entry, some isolation rooms are also
accessed through a wider wheeled-bed stretcher door. Release smoke at
all door entrances to isolation rooms.
4. So that the smoke is not blown into the isolation room, hold the smoke
bottle/tube parallel to the door so the smoke is released perpendicular
to the direction of airflow through the door undercut.
5. Position the smoke bottle/tube tight to the floor, centered in the
middle of the door jamb and approximately two inches out in front of
the door.
6. Release a puff of smoke and observe the resulting direction of airflow.
Repeat the test at least once or until consistent results are obtained.
7. Minimize momentum imparted to the smoke by squeezing the bulb or bottle
slowly. This will also help minimize the volume of smoke released.
8. Depending on the velocity of the air through the door undercut, the
smoke plume will either stay disorganized or it will form a distinct
streamline. In either case, the smoke will directionally behave in one
of three ways. It will:
a. go through the door undercut into the isolation room,
b. remain motionless, or
c. be blown back into the corridor.
Compliance with the intent of the CDC Guidelines for negative pressure
requires that the smoke be drawn into the isolation room through the
door undercut.
9. Release smoke from the corridor side of the door only for occupied TB
isolation rooms. If the room is unoccupied, also release smoke inside
the isolation room (same position as in Step No. 5) to verify that
released smoke remains contained in the isolation room (i.e., smoke as
a surrogate for TB droplet nuclei).
10. If photography is performed or videotaping, it is recommended that a
dark surface be placed on the floor to maximize contrast. Be aware
that most autofocusing cameras cannot focus on smoke.
Testing "As Used" Conditions:
Testing of negative pressure isolation rooms requires that the test
reflect "as-used" conditions. Consider the following use variables which
may affect space pressurization and the performance of the negative
pressure isolation room:
1. Patient toilet rooms are mechanically exhausted to control odors. The
position of the toilet room door may affect the pressure differential
between the isolation room and the corridor. Smoke-trail tests should
be performed with the toilet room door open and the toilet room door
closed. This will not be necessary if the toilet room door is normally
closed and controlled to that position by a mechanical door closer.
2. An open window will adversely affect the performance of a negative
pressure isolation room. If the isolation room is equipped with an
operable window, perform smoke-trail tests with the window open and
the window closed.
3. There may be corridor doors that isolate the respiratory ward or wing
from the rest of the facility. These corridor doors are provided in
the initial design to facilitate space pressurization schemes and/or
building life safety codes. Direct communication with the rest of the
facility may cause pressure transients in the corridor (e.g.,
proximity to an elevator lobby) and affect the performance of the
isolation room. Perform isolation room smoke-trail testing with these
corridor doors in their "as-used" position which is either normally
open or normally closed.
4. Isolation rooms may be equipped with auxiliary, fan-powered,
recirculating, stand alone HEPA filtration or UV units. These units
must be running when smoke-trail tests are performed.
5. Do not restrict corridor foot traffic while performing smoke-trail
tests.
6. Negative pressure is accomplished by exhausting more air than is
supplied to the isolation room. Some HVAC systems employ variable air
volume (VAV) supply air and sometimes VAV exhaust air. By varying the
supply air delivered to the space to satisfy thermal requirements,
these VAV systems can adversely impact the performance of a negative
pressure isolation room. If the isolation room or the corridor is
served by a VAV system you should perform the smoke test twice.
Perform the smoke test with the zone thermostat thermally satisfied and
again with the zone thermostat thermally unsatisfied thus stimulating
the full volumetric flowrate range of the VAV system serving the area
being tested.
Smoke:
Most smoke tubes, bottles and sticks use titanium chloride (TiCl(4)) to
produce a visible fume. There is no OSHA PEL or ACGIH TLV for this
chemical although it is a recognized inhalation irritant. Health care
professionals are concerned about releasing TiCl(4) around pulmonary
patients. The smoke released at the door undercut makes only one pass
through the isolation room and is exhausted directly outside. Isolation
room air is typically not "recirculated."
The CDC in the supplementary information to the 1994 TB Guidelines has
indicated that "The concern over the use of smoke is unfounded."
Controlled tests by NIOSH have shown that the quantity of smoke that is
released is so minute that it is not measurable in the air. Nonirritating
smoke tubes are available and should never-the-less be utilized whenever
possible.