Tuberculosis (TB) is a contagious disease caused by bacteria that can affect almost any part of the body but most often attack the lungs. Like the common cold, TB is spread through the air when an infected person coughs, sneezes, laughs or even sings.
When exposed to TB, most healthy people are able to fight the bacteria by sealing it off within the body, usually the lungs. These people have latent TB where they do not feel sick and cannot spread the bacteria to others. However, in some cases, the bacteria continue to multiply and make the person sick with active TB. A person with active TB can infect on average 10 to 15 people a year. If not treated properly, active TB can be fatal.