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(TB) n. an infectious disease caused by the bacillus Mycobacterium tuberculosis (first identified by Koch in 1882) and characterized by the formation of nodular lesions (tubercles) in the tissues.

In pulmonary tuberculosis – formerly known as consumption and phthisis (wasting) – the bacillus is inhaled into the lungs where it sets up a primary tubercle and spreads to the nearest lymph nodes (the primary complex). Natural immune defences may heal it at this stage; alternatively the disease may smoulder for months or years and fluctuate with the patient’s resistance. Many people become infected but show no symptoms. Others develop a chronic infection and can transmit the bacillus by coughing and sneezing. Symptoms of the active disease include fever, night sweats, weight loss, and the spitting of blood. In some cases the bacilli spread from the lungs to the bloodstream, setting up millions of tiny tubercles throughout the body (miliary tuberculosis), or migrate to the meninges to cause tuberculous meningitis. Bacilli entering by the mouth, usually in infected cows’ milk, set up a primary complex in abdominal lymph nodes, leading to peritonitis, and sometimes spread to other organs, joints, and bones (see Pott’s disease).

Tuberculosis is curable by various combinations of the antibiotics streptomycin, ethambutol, isoniazid (INH), rifampicin, and pyrazinamide. Preventive measures in the UK include the detection of cases by X-ray screening of vulnerable populations and vaccination with BCG vaccine of those with no immunity to the disease (the tuberculin test identifies which people require vaccination). The childhood immunization schedule no longer includes BCG vaccination at 10–14 years of age; vaccination now targets high-risk groups, such as immigrants from countries with a high incidence of TB. There has been a resurgence of tuberculosis in recent years in association with HIV infection. The number of patients with multidrug resistant TB has also increased due to patients not completing drug courses. Many centres have introduced directly observed therapy (DOT), in which nurse practitioners watch patients taking their drugs or administer the drugs.

Subjects: Medicine and Health.

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