Tuberculosis (TB) Tuberculosis 1. Identification-identification requires finding the organism Mycobacterium tuberculosis, the cause of TB. Respiratory symptoms should prompt an exam of the sputum, first by an acid-fast smear, then by culture and identification of the organism. The smear results should be available in hours. If positive, a diagnosis of TB should be assumed and treatment started. Final confirmation requires isolation of the culture.
Radiographs of the chest are helpful in the identification. 2. Agent-TB is caused by an infectious agent known as mycobacterium tuberculosis. 3. Occurrence-The number of TB cases had been declining by an average of 5% per year nationally since 1953.
This situation changed in 1985, when the incidence began to climb. In 1990, 25,701 TB cases were reported to the CDC. This represented a 9.4% increase over 1989 and was the largest for a single year since 1953. Reported cases increased 15.89% between 1985 and 1990. Although the AIDS epidemic has caused many of the changes, immigration, homelessness, drug abuse prison overcrowding, acts in public health funding, and drug resistance have also contributed to a situation that is out of control in some parts of the country.
And because TB is contagious, the risk extends beyond the groups traditionally considered high risk. TB has changed from a disease of older people to one of young adults and children. It has also evolved from a disease that struck across all racial and ethnic lines to one that is far more common among black and Latino populations than whites. The age distribution of new cases also point to a strong-but not absolute-link with AIDS. The greatest increase has been in people 24-44, the same group most seriously affected by HIV infection.
4. Reservoir-Only people were discussed but also animals. 5. Mode of Transmission-The agent infects the lungs by inhalation of infected droplets formed during coughing, singing or sneezing of an individual with the active form of the disease. 6. Incubation period-about 4-12 weeks 7. Period of communicability-As long as viable tubercle bacilli are being discharged in the sputum.
8. Susceptibility-The most hazardous period for development of clinical disease is the first 6-12 months after infection. But in the case of HIV infection, infection and development of TB symptoms is shorter than that in HIV negative patients with TB. According to some reports, HIV infected patients can develop primary progressive TB within a few weeks of exposure to M. tuberculosis. 9. Resistance-TB has changed bacteriologically.
Today in New York, as many as 20% of TB patients are infected with M. tuberculosis that is resistant to isoniazid (INH) and rifampin. TB experts believe that the drug resistance problem is due in part to poor compliance, which is bad among TB patients. In addition, widespread indifference to TB during the last two decades meant that no new specific anti-TB drugs entered the pipeline, monitoring for resistance lagged, and rapid diagnostic tests were not developed. 10. Methods of control-Controlling TB is very difficult.
A. Preventive measures-TB specialist overwhelmingly prefer the intradermal Mantoux test for screening. Candidates for screening include HlV-positive patients, close contacts of TB patients, people from countries with high TB rates or medical conditions that predispose to active TB, and residents of long-term-care facilities. Because of the high prevalence of anergy among HlV-infected patients, the CDC recommends administering companion tests for delayed-type hypersensitivity simultaneously with the Mantoux test. Most TB patients are treated with INH and rifampin as outpatients for 6 to 9 months.
Much of the responsibility for detection, prevention and treatment lies with our increasingly impacted and understaffed public health clinics throughout the country. The private sector also shares in an increasing demand for treatment of cases. More than 35% of the reported cases reported to the county health department come from sources other than public health facilities. Preventive therapy ordinarily consist of INH 300 mgs. daily for 6 to 12 months.
Where the risk of TB is very high, such as in those who are HlV- positive, 12 months is recommended. In all cases it is essential to rule out active TB before giving INH alone. The BCG (Bacillus of Calmette and Guerin) vaccine has been used in many parts of the world to prevent TB. Unless the BCG vaccine has been received within the past year, a positive TB skin test result in any person should be considered as indicating TB infection regardless of the remote history of a BCG vaccination. They should be assessed regarding TB disease.
B. Control of patients, contacts and the immediate environment-Of particular concern is the documented increase of disease in children. When TB is under control in a community, children should rarely be infected and essentially have no disease because they get the disease only from undetected adult cases. This indicates that adults with undetected TB are transmitting it to children. Another reason TB has remained endemic is because of the dramatic increase in the population and the changing demographics. Immigration of large numbers of persons from countries where TB is common has resulted in sustained numbers of new TB cases, despite the general decline in those born in the U.S. References Benenson, A.S., (1990).
Control of communicable disease in man (15th ed.). Washington D.C.: American Public Health Association. Davidson, P.T., Diferdinanando, G.T., Reichman, L.B., Snider,D.E. (May 15,1992). TB: coming soon to your town? Patient Care.