TB is caused by bacteria (Mycobacterium tuberculosis) that mostly affect the lungs. TB is preventable, treatable and curable.
TB is spread through the air. When people with lung TB cough, sneeze or spit, they send TB germs into the air. To become infected, a person needs to inhale only a few of the germs.
About one-third of the world’s population has latent TB. With latent TB, people have been infected by TB bacteria but are not (yet) sick with the disease and cannot transmit it. If they are diagnosed, the latent form of the disease can be treated and cured. However, since they are a-symptomatic most people do not know they have TB.