Tuberculosis (TB) is a contagious infectious disease caused by the bacterium Mycobacterium tuberculosis. It most commonly affects the lungs but can also involve other parts of the body such as the spine, brain, or kidneys. TB spreads through the air when an infected person coughs or sneezes, though it usually requires prolonged close contact for transmission. Not everyone who is infected becomes sick—some people carry the bacteria without showing symptoms.
TB develops in stages, including initial infection, latent (inactive) TB, and active TB disease. In latent TB, the bacteria remain dormant in the body without causing illness or spreading to others. Active TB, however, causes symptoms and is contagious, requiring prompt medical treatment. Early diagnosis and proper care are essential to control the infection, prevent complications, and stop the spread of tuberculosis.