Tuberculosis

Around 10 million people suffer from tuberculosis worldwide each year and around 1.5 million people die from the disease. Tuberculosis is caused by Mycobacterium tuberculosis, a bacterium that is transmitted between humans by those with pulmonary tuberculosis. Exposure can lead to prolonged asymptomatic infection (‘latent’ tuberculosis), or ‘active’ tuberculosis with pulmonary (80%) or extra-pulmonary disease (20%). Latent tuberculosis is identified by demonstrating T-cell-mediated immune reactivity to M. tuberculosis antigens, either by the intra-dermal injection of purified protein derivative (PPD) (e.g. Mantoux skin test) or by the interferon gamma release assays (IGRAs) performed on peripheral blood. Active tuberculosis diagnosis requires demonstration of M. tuberculosis in a specimen from an affected tissue by microscopy, rapid molecular methods (e.g. GeneXpert MTB/RIF test), or culture. Latent tuberculosis can be treated with 3 months of isoniazid and rifampicin or rifapentine. Active tuberculosis treatment always requires combination drug therapy, usually for at least 6 months. New, all-oral, 6-month regimens now provide effective treatment of multi-drug resistant tuberculosis. Tuberculosis can be prevented by reducing transmission and treating latent infection. The BCG vaccine prevents disseminated tuberculosis in very young children; but new vaccines are being sought to prevent the disease in older children and adults.