It can affect any organ in the body but most commonly affects the lungs. TB is spread person to person when the bacteria is coughed into the air by one person and is inhaled by another person. In most people, the immune system, which is the body's defense against germs and other invaders, is able to control the infection. In these cases, the infection may cause few or no symptoms. Children younger than age 4, teenagers, elderly people, and those who have problems with their immune systems may develop a more severe infection.
Severe infections can occur in every part of the body, including the brain.
Other symptoms may occur if the infection spreads outside of the lungs, depending on where the infection goes. For example, seizures and vomiting can occur with a brain infection. Pain may occur if the infection gets into the bones. Blood may be seen in the urine if the infection gets into the kidneys. Exposure to a person with tuberculosis is the cause of the infection.