Tuberculosis, commonly known as TB, is a communicable disease caused by M. tuberculosis. The organism is carried in airborne particles known as droplet nuclei that are generated when a person with active disease coughs, laughs, sings or speaks. The particles are so small (1 - 5u) that normal air currents may keep them airborne and can spread them throughout a room.
How Does TB Infect A Person?
The tubercle bacillus reaches the tiny air sacs of the lung when droplet nuclei are inhaled. The organisms initially establish themselves and may spread throughout the body. Two to 10 weeks after the initial infection with M. tb, the body's immune system contains the infection. The only evidence of infection is a positive skin test(Mantou). In a small proportion (<10%) of individuals, the infection is not contained by the body's immune system and progressive tuberculosis (usually in the lungs) develops.
Who Is At Risk For Developing Active TB?
The risk of progression to active disease is increased in conditions of poor health, poor nutrition, overcrowding and an innate lack of resistance to tuberculosis. Immunocompromised patients, especially those with HIV, cancer, and transplants are at markedly increased risk for developing active tuberculosis.
Why Is TB Becoming A Problem Again?
Tuberculosis does appear to be making a comeback again in industrialized countries. In the US in 1991, more than 26,000 cases were reported, representing a 16% increase since 1984. In some large US centres, a 35% increase has been noted. In Ontario, the number of reported cases in 1986 was 644 and in 1992 was 800 with a rate of ~ 8/100,000. The increase in TB in the U. S. has been attributed to several factors, including an increase in the number of immunosuppressed people with TB (including HIV infection), Homelessness, and the appearance of drug-resistant strains of M. tuberculosis. Three outbreaks of TB have recently occurred in New York City in health care facilities. Factors identified in these outbreaks facilitating spread included the presence of drug resistant TB strains, a long delay in diagnosis and treatment, and poor application of isolation precautions.
What Strategies Are Employed At TTH Regarding Tuberculosis?
Strategies employed for dealing with tuberculosis include early identification and treatment of active cases of tuberculosis; Liberal use of isolation for individuals with know or suspected tuberculosis; reduction of environmental contamination by droplet nuclei; active ongoing surveillance; and appropriate decontamination of critical and semi-critical items. Current isolation practices for preventing the spread of TB may be found in the Infection Control Manual in the Disease Specific Information Policy 60.15. The manuals are available in every department and on all nursing units.
Further Reading:
Edlin, B.R.; Tokars, J.I.; Griego, M.H. An outbreak of multidrug-resistant tuberculosis among hospital patients with the Acquired Immunodeficiency Syndrome. New England Journal of Medicine: 326; 1514-21, 1992
Beneson, Abram(Editor). Control of Communicable Diseases in Man. Fifteenth Edition, American Public Health Association: 1990; p.p. 457-465.
Guidelines for the Prevention and Transmission of TB in Health Care. MMWR, December 1990
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