Killer Diseases: How the body reacts to tuberculosis
Tuberculosis (TB) is caused by a bacterium (Mycobacterium tuberculosis) that is spread through the air when infected people cough or sneeze.
The disease most often affects the lungs but it can infect any part of the body, including the bones and the nervous system.
Most people who are exposed to TB never develop symptoms, since the bacteria can live in an inactive form in the body, but if the immune system weakens, such as in malnourished people, people with HIV or the elderly, TB bacteria can become active.
Around 10 percent of people infected with TB will develop active TB and become contagious at some point in their lives.