Tuberculosis (TB) is an infectious disease caused by the bacterium Mycobacterium tuberculosis. It primarily affects the lungs but can also impact other parts of the body such as the kidneys, spine, and brain. TB is transmitted through the air when a person with active TB disease of the lungs or throat coughs, sneezes, speaks, or sings, releasing tiny droplets containing the bacteria. People nearby can inhale these droplets and become infected.