Summary. The infectiousness of patients who have TB is directly related to the number of tubercle bacilli that they expel into the air. Infectiousness usually declines very rapidly after adequate therapy is started. The main goal of an infection control program is to detect TB disease early and to isolate and treat promptly persons who have TB. The infection control program should involve three types of controls--administrative controls, engineering controls, and personal respiratory protection. Administrative controls (e.g., the prompt detection of suspected cases, isolation of infectious patients, and appropriate treatment) are the primary strategy for infection control. Administrative controls include training and education and TB screening for health care workers. In addition, three types of engineering controls may be used to prevent the transmission of TB is health care facilities: ventilation, high-efficiency particulate air (HEPA) filtration, and ultraviolet germicidal irradiation (UVGI).
In places where administrative and engineering controls may not fully protect health care workers from infectious droplet nuclei, health care workers should use personal respirators. Precautions to prevent airborne transmission are particularly important during and immediately after procedures that stimulate coughing (e.g., sputum collection, bronchoscopy, and aerosolized pentamidine treatments). Such procedures should be carried out in rooms designated for these procedures and with appropriate ventilation. Coordination with the health department is necessary in order to report all confirmed or suspected TB patients, conduct contact investigations, and plan for follow-up care for patients known to have or suspected of having TB.
Infectiousness is directly related to the number of tubercle bacilli expelled into the air. In general, persons who have or who are suspected of having pulmonary or laryngeal TB should be considered infectious if (1) they are coughing, they are undergoing cough-inducing or aerosol-generating procedures, or their sputum smears contain acid-fast bacilli; and (2) they are not receiving therapy, have just started therapy, or have a poor clinical or bacteriologic response to therapy.
Patients are not considered infectious if they meet all the following criteria:
Persons with extrapulmonary TB are usually not infectious. However, in several instances, TB has been transmitted from a draining skin or tissue abscess containing M. tuberculosis.
Patients with TB disease should be closely monitored for relapse. Smear examinations should be done regularly (e.g., every 1 to 2 weeks) while the patient is hospitalized. Persistent infectiousness is usually due to drug resistance or the patient's failure to take medication as prescribed. These possibilities should be considered for any patient who does not clinically respond to therapy within 2 to 3 weeks.
In patients with drug-resistant TB, infectiousness may last several weeks or even months. In these patients, the response to treatment should be closely monitored, and TB isolation should be maintained until infectiousness is ruled out. Continued isolation throughout hospitalization should be considered for patients with multidrug-resistant TB because these patients are more likely to experience treatment failure or relapse, which may prolong infectiousness.
An effective TB infection control program requires the early detection, isolation, and treatment of persons with infectious TB. The primary emphasis of the infection control plan should be on achieving these three goals through a hierarchy of control measures, including
All health care facilities must have guidelines for the prompt detection of suspected TB cases. These guidelines should include assigning supervisory responsibility for TB control.
In general, clinicians should suspect TB in any patient who has a persistent cough, bloody sputum, night sweats, fever, weight loss, or loss of appetite. The index of suspicion should be very high in areas or among groups of patients in which the prevalence of TB is high. In ambulatory and inpatient settings, designated personnel should develop a protocol for the early detection of persons with infectious TB, basing it on the prevalence and characteristics of TB in the population served.
In an outpatient setting, patients who have signs or symptoms of TB should be moved to an area away from other patients (preferably into a TB isolation room) and promptly given a diagnostic evaluation. These patients should be given a surgical mask and instructed to keep it on; they should also be given tissues and asked to cover the nose and mouth when coughing or sneezing.
After a thorough and timely diagnostic evaluation (see Diagnosis of TB), patients for whom TB has been confirmed or is suspected should start appropriate therapy at once.
TB should be considered in HIV-infected patients with undiagnosed pulmonary disease. If TB is suspected, appropriate precautions to prevent airborne transmission should be taken unless infectious TB is ruled out.
In hospitals and other inpatient settings, patients known to have TB or suspected of having TB should be placed in a TB isolation room right away. All TB isolation rooms must have negative pressure relative to other parts of the facility (air flow from the corridors into the isolation room) and must be checked periodically to ensure proper air flow.
Patients should be educated about the transmission of TB, the reasons for TB isolation, and the importance of staying in their rooms. 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 persons as possible should enter the TB isolation room, and anyone entering the room should wear respiratory protection (see Personal Respirators).
Because TB is transmitted through the air rather than by fomites or direct contact, the sterilization of personal items or eating utensils and the cleaning of walls are unnecessary.
Health care workers, including home health nurses and emergency medical technicians, should be included in a TB screening and prevention program. This means tuberculin skin testing for all health care workers upon employment and at intervals determined by their risk of exposure thereafter. Any worker who develops symptoms of TB disease or whose tuberculin skin test result converts to positive should be evaluated promptly.
In addition, 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 employee skin testing program.
Health care facilities should work closely with the health department to report all confirmed or suspected cases of TB, to ensure that contact investigations are carried out for all cases, and to develop an appropriate discharge plan for TB patients or persons suspected of having TB.
Patients who are suspected of having infectious TB may be discharged to their home after starting TB therapy, even though they may still be infectious. It is important to note that after treatment has started, persons who have TB are less likely to transmit the disease to members of their household. However, before the patient is discharged to home, clinicians and discharge planners should consider whether any household members were previously exposed or are at very high risk for TB disease if infected (e.g., HIV infected or otherwise severely immunocompromised persons or children 5 years of age or younger).
Engineering controls are based primarily on the use of adequate ventilation systems; these may be supplemented with high-efficiency particulate air (HEPA) filtration and ultraviolet germicidal irradiation (UVGI) in high-risk areas. These strategies are designed to reduce the concentration of infectious droplet nuclei in the air, to prevent the dissemination of droplet nuclei throughout the facility, or to render droplet nuclei noninfectious by killing the tubercle bacilli they contain.
In isolation rooms, ventilation systems are necessary to maintain negative pressure and to exhaust the air properly. Isolation rooms should be monitored daily when in use to ensure the negative pressure maintained. Isolation room doors should be kept closed, except when patients or personnel must enter or exit the room, in order to maintain negative pressure. Ventilation systems can also be designed to minimize the spread of TB in other areas of the health care facility.
HEPA filters can be used in ventilation systems to remove droplet nuclei from the air. These filters can be installed in ventilation ducts to filter air for recirculation into the same room or recirculation to other areas of a facility. The effectiveness of portable HEPA filtration units has not been adequately evaluated. All HEPA filters must be carefully installed and meticulously maintained to ensure adequate function.
UVGI, or ultraviolet lighting, may kill M. tuberculosis contained in droplet nuclei. Because exposure to ultraviolet light can be harmful to the skin and eyes, the lamps must be installed in the upper part of rooms or corridors or placed in exhaust vents. The effectiveness of UVGI in preventing the transmission of TB is not known.
In some settings--for example, TB isolation rooms and rooms where cough-inducing procedures are done--administrative and engineering controls may not fully protect health care workers from infectious droplet nuclei. Health care workers should use personal respirators to filter out droplet nuclei in these settings. They should also use personal respirators when visiting the home of an infectious TB patient. A respiratory protection program that teaches health care workers how and when to use personalrespirators should be included in all infection control programs.
Precautions to prevent the airborne transmission of tubercle bacilli are particularly important during and immediately after procedures that stimulate coughing (e.g., sputum collection, sputum induction, bronchoscopy, and aerosolized pentamidine treatments) by persons at risk for TB. Persons who carry out these procedures should wear personal respirators, and the procedures should be done in rooms or booths with negative air pressure in relation to adjacent rooms or hallways. The air from these rooms should be exhausted directly to the outside and away from intake sources.
For further details on the planning and implementation of an infection control program, please refer to the CDC's latest published infection control guidelines.