what is tuberculosis caused by

Tuberculosis (TB) is caused by a bacterium called Mycobacterium tuberculosis. The bacteria usually attack the lungs, but they can attack any part of the body such as the kidney, spine, and brain. TB spreads through the air when infected people cough, sneeze, or spit, putting tiny droplets with the germs into the air. Another person can then breathe in the droplets, and the germs enter the lungs. People with active TB disease in the lungs or voice box can spread the disease. TB is preventable and curable, but if not treated properly, TB disease can be fatal.