Self-Study Modules on Tuberculosis
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5: Infectiousness and Infection Control
Where Can TB Be Spread?
TB is a communicable disease. It can be spread in many places, such
as homes or worksites. On average, about 30% of people who spend a
lot of time with someone who has infectious TB disease (close contacts)
become infected with M. tuberculosis. However, TB patients
vary in their infectiousness; some infect most or all their close
contacts, whereas others infect few or none of their contacts.
TB can also be transmitted in health care facilities, such as hospitals
and clinics. TB is most likely to be transmitted when health care
workers and patients come in contact with patients who have unsuspected
TB disease, who are not receiving adequate treatment, and who have
not been isolated from others. Several recent outbreaks of TB in
health care facilities, including outbreaks of multidrug-resistant
TB, have heightened concern about the spread of TB in these facilities.
The transmission of TB to HIV-infected people is of particular concern
because these persons are at high risk of developing TB disease
if infected. All health care facilities should take measures to
prevent the spread of TB.
What Are the Parts of an Effective Infection Control Program?
The main goal of an infection control program is to detect
TB disease early and to promptly isolate and treat
people who have TB disease. The infection control program
should involve three types of controls:
- Administrative controls
- Engineering controls
- Personal respiratory protection
Administrative controls. Administrative controls
mean establishing and following guidelines for
Other administrative control measures include
- Promptly detecting patients who have TB disease
- Placing these patients in an area away from other patients and
giving them a diagnostic evaluation
- Treating patients who are likely to have TB disease
To detect patients who have TB disease as soon as possible,
clinicians and other health care workers should suspect TB disease
in a patient who has any of these symptoms:
- Making sure that health care workers are following guidelines
for preventing the spread of TB
- Educating, training, and counseling health care workers about
- Screening health care workers for TB infection and disease
In areas where TB is very common, staff of local health care facilities
should be especially alert for TB. Health care workers who admit patients
to the facility should be trained to ask appropriate questions to
help detect patients who have signs or symptoms of TB disease.
- A persistent cough
- Bloody sputum
- Weight loss or loss of appetite
- Night sweats
Patients who have signs or symptoms of TB disease should be placed
in an area away from other patients (preferably in a TB
isolation room) and promptly given a diagnostic evaluation.
These patients should be given a surgical mask (Figure 5.1) and
instructed to keep it on. They should also be given tissues and
asked to cover their nose and mouth when coughing or sneezing, even
when in an area away from others.
Figure 5.1 TB patient wearing a surgical mask. This is a picture
of a TB patient wearing a surgical mask.
In hospitals and other inpatient settings, patients known to have
TB disease or suspected of having TB disease should be placed in
a special TB isolation room right away. TB isolation
rooms are rooms in the facility that have special characteristics
to prevent the spread of droplet nuclei expelled by a TB patient.
One characteristic of TB isolation rooms is that they are at negative
pressure relative to other parts of the facility. Negative
pressure means that air flows from the corridors into the
isolation room. This way, contaminated air cannot escape
from the isolation room to other parts of the facility. Air from
the isolation room can be exhausted directly to the outdoors, where
any infectious droplet nuclei will be diluted in the outdoor air
and killed by the sunlight. Alternatively, the air can be passed
through a special filter that removes all of the droplet nuclei
before the air is returned to the general circulation (see HEPA
filters, in the Engineering Controls Section).
The room should have at least six air changes per hour. The door
must be kept closed in order to maintain negative pressure, and
the room must be checked periodically to make sure that it remains
at negative pressure.
Patients suspected of having TB disease should be given a diagnostic
evaluation as soon as possible. This means a medical history, a
tuberculin skin test, a chest x-ray, and the collection of specimens
for a bacteriologic examination (see
Module 3, Diagnosis of Tuberculosis Infection and Disease).
It is important that laboratories use the most rapid diagnostic
methods available. In outpatient settings where a diagnostic evaluation
cannot be completed, patients who have symptoms of TB should be
referred to a facility capable of doing the evaluation.
Patients who are likely to have TB should start appropriate
treatment at once.
Patients should be educated about the transmission of TB, the reason
for TB isolation, and the importance of staying in their room. Every
effort should be made to help the patient follow the isolation policy
— including the use of incentives, such as providing telephones
or televisions or allowing special dietary requests. As few people
as possible should be allowed to enter the TB isolation room, and
anyone entering should wear respiratory protection (see
Personal Respiratory Protection).
Training and education. All health care workers
should be educated about the basic concepts of TB transmission and
pathogenesis, infection control practices, the signs and symptoms
of TB, and the importance of participating in the skin testing program
for health care workers.
TB screening for health care workers. Health care
workers who may be exposed to TB should be included in a TB screening
and prevention program. This means two-step tuberculin skin testing
upon employment and at least once a year thereafter. Any worker
who develops symptoms of TB disease or whose tuberculin skin test
reaction converts to positive should be evaluated promptly.
Study Questions 5.4-5.7
5.4 In what circumstances is TB most likely to be transmitted
in health care facilities?
5.5 What is the main goal of an infection control program?
What three types of controls should this program involve?
5.6. What would make a health care worker suspect that
a patient has TB disease?
5.7 What should be done when a health care worker suspects
that a patient has TB disease?
Study Questions 5.8-5.9
5.8 What is a TB isolation room? What are the important
characteristics of an isolation room?
5.9 How often should health care workers who may be exposed
to TB be tuberculin skin tested?
Case Study 5.2
You are checking patients into the TB clinic. An elderly
man comes to the desk and says he was told to come and get
checked because one of his friends has TB. You notice that
he looks sick and is coughing frequently. The waiting room
is full of patients, and you know it will probably be more
than an hour before the physician can see him.
Three types of engineering controls are used to prevent the transmission
of TB in health care facilities: ventilation, high-efficiency particulate
air (HEPA) filtration, and ultraviolet germicidal irradiation. In
isolation rooms, ventilation systems are necessary
to maintain negative pressure and to exhaust the air properly. These
systems can also be designed to minimize the spread of TB in other
areas of the health care facility. HEPA filters are
special filters that can be used in ventilation systems to help
remove droplet nuclei from the air. Ultraviolet germicidal
irradiation (UVGI), or the use of special lamps that give
off ultraviolet light, is used to kill the tubercle bacilli contained
in droplet nuclei. However, exposure to ultraviolet light can be
harmful to the skin and eyes of humans, so the lamps must be installed
in the upper part of rooms or corridors or placed in exhaust ducts.
HEPA filters and UVGI should be used in conjunction with other infection
Personal respiratory protection.
In some settings, administrative and engineering controls may not
fully protect health care workers from infectious droplet nuclei.
These settings include
- TB isolation rooms
- Rooms where cough-inducing procedures are done
- Ambulances and other vehicles transporting infectious TB patients
- The homes of infectious TB patients
Health care workers should use personal respirators,
or special masks designed to filter out droplet nuclei, in these
settings (Figures 5.2 and 5.3). Health care workers should be taught
how and when to use personal respirators.
Figures 5.2 and 5.3 Health care worker wearing a personal respirator.
The personal respirator in these photographs is specially designed
to filter out droplet nuclei. This is a picture of a health care
worker wearing a personal respirator which are used to filter out
Cough-inducing procedures. Cough-inducing procedures
should be done in special isolation rooms or booths. This will prevent
any droplet nuclei that are expelled during the procedure from reaching
other parts of the facility. Some examples of cough-inducing procedures
are sputum induction, bronchoscopy, and the administration of aerosolized
medications (such as pentamidine, which is given to patients with
HIV infection to prevent Pneumocystis carinii pneumonia).
Study Questions 5.10-5.12
5.10. How do ventilation systems help prevent the spread
5.11. Give four examples of settings where personal respirators
should be used.
5.12. Where should sputum induction, bronchoscopy, and
other cough-inducing procedures be done?
What Is the Role of the Health Department in Infection Control?
The health department should work closely with health care facilities
to help them report confirmed or suspected TB cases as quickly as
possible. When the health department receives a report of a TB case
or suspected case, it should begin a contact investigation.
Also, the health department and the health care facilities should
work together to make sure there is a plan for TB patients to receive
follow-up care after they are discharged. Finally, the health department
should be able to help health care facilities with screening, surveillance,
outbreak investigations, and other aspects of a TB infection control
Infection Control in Residential Facilities
All residential facilities where TB patients receive care should
establish and follow an infection control program. These residential
facilities may include nursing homes, correctional facilities, homeless
shelters, drug treatment centers, and other places. As in health
care facilities, the main goal of the infection control program
should be to detect TB disease early and arrange for the isolation
and treatment of suspected TB patients. CDC has published guidelines
for controlling TB in certain types of residential facilities (see
Infection Control in the Home
Patients who are suspected of having infectious TB are frequently
sent home after starting treatment, even though they may still be
infectious. This is because people with TB disease are most likely
to transmit TB to members of their household before
TB has been diagnosed and treatment has started. However, TB patients
and members of their household can take steps to prevent the spread
of TB in their home. For example, TB patients should be instructed
to cover their mouth and nose with a tissue when coughing or sneezing.
Health care workers who visit TB patients at home should take these
precautions to protect themselves from the spread of TB:
- Instruct patients to cover their mouth and nose with a tissue
when coughing or sneezing
- Wear a personal respirator when visiting the home of an infectious
TB patient or when transporting an infectious TB patient in a
- When it is necessary to collect a sputum specimen in the home,
collect the specimen in a well-ventilated area, away from other
household members; if possible, the specimen should be collected
- Participate in a TB screening and prevention program
Study Questions 5.13-5.14
5.13. How can the health department help health care facilities
in preventing the spread of TB?
5.14. What precautions should a health care worker take
when visiting the home of a TB patient who may be infectious?
Case Study 5.3
You are sent to deliver directly observed therapy to a
woman who started treatment last week for suspected pulmonary
TB. Her sputum smear results are not back yet. You are asked
to collect another sputum specimen while you are at the
- What precautions should you take?