TB infection vs. TB disease
There is a difference between TB infection and TB disease. When a person has been exposed to someone with TB disease and has breathed in the TB germs, that person may become infected with TB. In most cases, people with healthy immune systems can contain the infection at that point and not become ill with TB disease. A person with TB infection only (positive TB skin test but normal chest x-ray) is not sick and is not contagious to others. TB medicine can help kill the bacteria and prevent the development of TB disease in the future.
However, if a person with TB infection does not take preventive medicine, the bacteria may grow and cause active TB disease. TB symptoms may include a constant cough that lasts two or more weeks, chest pain, weakness, and loss of appetite. When a person has active TB disease, the individual may be contagious and cause infection in other people, particularly those with whom they spend the most time.
Someone with active TB disease will need to take several TB medicines for many months in order to become well and not infect others. However, they may no longer be infectious after a few weeks of medicine and would be able, once cleared by the Health Department, to return to work and normal activities while they are completing their TB treatment. People can have active TB in any organ of the body, but it is only infectious to others when it is in the lungs or larynx.