The most common form, pulmonary tuberculosis (formerly known as ‘consumption’), is caused by inhalation of the bacteria. It was widespread in 19th-century Europe, and still causes millions of deaths each year in developing countries. The disease can affect other parts of the body, notably the bones and joints and the central nervous system. Its spread is countered by vaccination and by the pasteurization of milk to prevent transmission from cattle. It was once considered incurable, but early X-ray diagnosis permits its arrest by drugs and surgery.