Tuberculosis (TB) is caused by a bacterium called Mycobacterium tuberculosis. The bacteria usually attack the lungs, but TB bacteria can attack any part of the body such as the kidney, spine, and brain. Not everyone infected with TB bacteria becomes sick. As a result, there are two TB-related conditions exist: latent TB infection (LTBI) and TB disease. If not treated properly, TB disease can be fatal. TB bacteria are spread through the air from one person to another. The TB bacteria are put into the air when a person with TB disease of the lungs or throat coughs, speaks, or sings. People nearby may breathe in these bacteria and become infected. When a person breathes in TB bacteria, the bacteria can settle in the lungs and begin to grow. From there, they can move through the blood to other parts of the body, such as the kidney, spine, and brain. People with TB disease are most likely to spread it to people they spend time with every day. This includes family members, friends, and coworkers or schoolmates.TB bacteria can live in the body without making you sick. This is called latent TB infection. In most people who breathe in TB bacteria and become infected, the body is able to fight the bacteria. People with latent TB infection have no symptoms; don’t feel sick; can’t spread TB bacteria to others; usually have a positive TB skin test reaction or positive TB blood test; may develop TB disease if they do not receive treatment for latent TB infection. TB disease in the lungs may cause symptoms such as a bad cough that lasts 3 weeks or longer, pain in the chest and coughing up blood or sputum (phlegm from deep inside the lungs). Other symptoms of TB disease are weakness or fatigue; weight loss; no appetite; chills; fever and sweating at night. Those at high risk for developing TB disease include people with HIV infection; people who became infected with TB bacteria in the last 2 years; babies and young children; people who inject illegal drugs; people who are sick with other diseases that weaken the immune system; elderly people and people who were not treated correctly for TB in the past. There are two kinds of tests that are used to detect TB bacteria in the body: the TB skin test (TST) and TB blood tests. A positive TB skin test or TB blood test only tells that a person has been infected with TB bacteria. Other tests, such as a chest x-ray and a sample of sputum, are needed to see whether the person has TB disease. TB disease can be treated by taking several drugs for 6 to 9 months.
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