This article is from the Childhood Vaccinations FAQ, by Lynn Gazis-Sax email@example.com with numerous contributions by others.
Tuberculosis is a chronic bacterial infection that is spread by
inhaling droplets sprayed into the air by someone infected with TB (it
can also be spread through unpasteurized milk). It isn't as contagious
as a cold (you need to inhale a higher concentration of the droplets
to catch it). The disease most commonly affects the lungs, the bones
of the spine or large joints, and the kidneys, but can reach almost
any organ of the body.