Mycobacterium tuberculosis (M. tuberculosis) is a bacterium that causes tuberculosis (TB) in humans. TB is a disease that primarily affects the lungs, although it can attack other parts of the body. It spreads much like a cold or the flu — through the expelled airborne droplets from a person with infectious TB.
When inhaled, the bacterium can settle in the lungs, where it begins to grow. If not treated, it can spread to areas such as the kidneys, spine, and brain. It can be life-threatening.
According to the Centers for Disease Control and Prevention (CDC)Trusted Source, more than 9,000 new cases of TB were reported in the United States in 2017.
In fact, only 5 to 10 percentTrusted Source of those carrying the bacterium will actually develop a case of active, contagious tuberculosis in their lifetimes. That normally happens when the lungs are already damaged from diseases like chronic obstructive pulmonary disease (COPD) and cystic fibrosis or from smoking.