A tuberculosis bacterium 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.

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.

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 this germ, 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 tuberculosis infection.

People with latent tuberculosis infection usually have positive purified protein derivative (PPD) or tuberculin skin test results, but they do not have symptoms of active tuberculosis and they are not infectious.

Transmission of M. tuberculosis is a recognized risk to patients and health care providers 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.

It is worth to mention that several 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 increase the risk for nosocomial (hospital acquired infections) and occupational transmission of M. tuberculosis.

Increased incidence of tuberculosis has been observed in immunosuppressed persons, particularly those infected with HIV. Transmission of M. tuberculosis to HIV-infected persons is of particular concern because these persons, are at high risk for developing active tuberculosis if they become infected with the bacteria.

Therefore, 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 tuberculosis infection control program should be assigned to a designated person or group of persons, who should be given the authority to implement and enforce tuberculosis infection control policies.

An effective tuberculosis infection-control program requires early identification, isolation, and treatment of persons who have active tuberculosis. The primary emphasis of tuberculosis infection control plans in health care facilities, should be achieving these three goals by the application of a hierarchy of control measures, including the use of administrative measures to reduce the risk for exposure to persons who have infectious tuberculosis.

The use of engineering controls to prevent the spread and reduce the concentration of infectious droplet nuclei is an admirable measure. Another important measure to mention includes use of personal respiratory protective equipment in areas where there is still a risk for exposure to M. tuberculosis. In this case it is very necessary to create rooms for tuberculosis isolation.

Implementation of a tuberculosis infection control program requires risk assessment and development of a tuberculosis infection control plan such as early identification, treatment, and isolation of infectious patients.

Like we have mentioned already, there is need for effective engineering controls, an appropriate respiratory protection program; health work training on tuberculosis infection and spread. Other conditions such as education, counseling, and screening as well as evaluation of the program’s effectiveness are valuable.

Although completely eliminating the risk for transmission of M. tuberculosis in all health care facilities may not be possible, adherence to the above mentioned recommendations should reduce the risk to persons in health care settings.

 Recent scientific research, has strongly linked nosocomial tuberculosis outbreaks that have demonstrated substantial morbidity and mortality among patients and health care practitioners. This has been associated with incomplete implementation of the tuberculosis control measures for prevention of tuberculosis in Health Care Facilities with Special Focus on HIV.

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