Tuberculosis (TB) is a disease caused by infection with the bacterium mycobacterium tuberculosis. TB primarily affects the lungs but can also affect other body parts including the kidney, spine, and brain. Left untreated, tuberculosis can be fatal. TB was once the leading cause of death in the United States (when it was commonly called consumption) and it still causes nearly 2 million deaths each year worldwide. However, with proper care, most cases of tuberculosis can be treated.

Infection with m. tuberculosis is very common; scientists estimate that about one-third of the world’s population may be infected. In most of these people, the infection is dormant, held in check by the body’s immune system. Such people are said to have latent TB infection and they have no symptoms and cannot spread the disease. However, in some people, the infection becomes active and causes TB disease.