The TB bacterium destroys body tissues, particularly lung tissue, when TB disease is active. During the primary stage of TB infection most people have no symptoms even as their body is producing antibodies. If a person is normally healthy, the body's natural defenses produce antibodies to fight the infection, the bacteria are walled off within a capsule, and the infection does not progress. The bacteria are still alive, however, and can escape and become active later especially if the body's immune system becomes impaired or there are conditions of poor nutrition or use of certain drugs. TB disease occurs when the body's defenses are not successful in encapsulating the bacterium and they begin destroying body tissue, particularly lung tissue.
Treatment includes taking prescribed antibiotic drugs for several months to kill the bacteria.