Tuberculosis is a disease caused by TB bacteria. Someone infected with TB bacteria can spread it to another by coughing, sneezing, singing, or talking in a poorly ventilated area. People have to breathe in enough of the bacteria to get sick. For this reason, TB spreads between close contacts, rather than between passing strangers. Most healthy people don’t get sick from TB. Instead, they get what’s called latent TB. Their immune systems fight off the bacteria so that it goes into a dormant state and doesn’t reproduce itself in the body. People with latent TB don’t get symptoms and don’t spread the germs to others. For this reason, if you were in contact with someone with latent TB, you don’t need to get tested for TB. But latent TB can turn into active TB in the future. If a health condition or treatment weakens the immune system, the latent TB can begin to multiply. Then, the person develops active TB. TB can lead to lesions in the lungs that make it difficult to breathe. Without treatment, it can be fatal. Doctors treat TB with antibiotics, taken over months.