Tuberculosis

Tuberculosis is caused by bacteria, most often Mycobacterium tuberculosis. The lungs are the most common site, but TB disease can also affect organs such as the kidneys, spine and brain. The infection spreads through the air when a person with infectious TB of the lungs or throat releases bacteria by coughing, speaking or singing and another person breathes them in.

After infection, many people do not become ill. In latent or inactive TB infection, bacteria remain in the body without causing symptoms, and the person cannot transmit TB to others. In some people, bacteria later multiply and cause active TB disease; progression is more likely when immune defenses are weakened. Active disease usually affects the lungs, but may occur elsewhere in the body. People with infectious TB of the lungs or throat may pass the bacteria to others.

Pulmonary TB can cause a prolonged cough, chest pain, coughing up blood or sputum, fever, night sweats, fatigue and weight loss. Symptoms may develop gradually, and the signs of TB affecting other organs depend on the site involved. Tests for TB infection include blood tests and the tuberculin skin test; a positive result or symptoms call for further medical evaluation to determine whether active disease is present. Evaluation for disease can include clinical assessment, imaging and laboratory testing of appropriate samples. The World Health Organization recommends rapid diagnostic tests as initial tests for people with signs and symptoms of TB.

TB disease is treated with combinations of antibiotics taken over a prescribed course; preventive treatment can also be offered to some people with TB infection to reduce the risk of progression to disease. The choice and duration of treatment depend on the form of TB and whether the bacteria are drug-resistant. Completing treatment as directed is important: inadequate or interrupted treatment can contribute to resistance, and drug-resistant TB requires different medicines and careful management. Prevention includes identifying and treating disease, testing people at elevated risk, and measures to reduce exposure in settings where transmission may occur. The BCG vaccine is used in some countries, especially for young children, to protect against severe forms of TB disease.