Tuberculosis is a chronic infection caused by the bacteria Mycobacterium tuberculosis (and occasionally other variants of Mycobacterium). It usually involves the lungs, but other organs of the body can also be involved.

Today, tuberculosis (TB) tends to be concentrated among inner city dwellers, ethnic minorities and recent immigrants from areas of the world where the disease is still common. Alcoholics, who are often malnourished, are at high risk of developing the disease, as are people...