Tuberculosis (TB) is a highly contagious disease. It’s caused by an infection of bacteria called Mycobacterium tuberculosis (Mtb). Exposure to Mtb can result in latent TB, which means you’re infected but have no symptoms. Latent TB can eventually become active TB, which must be treated with medication. There are two types of tests used to diagnose TB: a blood test and a skin test. Your results from either test will not reveal whether you have latent or active TB.