It can be spread through close, prolonged or regular exposure to someone with active TB disease in the lungs or throat who is coughing or sneezing. Most people who breathe in the TB bacteria do not develop TB because their immune system fights it. Some bacteria may remain alive but not growing. This is called inactive or latent TB infection.
Medicine is available to prevent TB from becoming active.
Those with latent infection have no symptoms, have a normal chest x-ray, cannot spread TB germs and do not feel sick. They usually have a positive skin test and may develop active TB disease later in life. TB bacteria become active if the body's immune system cannot stop them from growing. A physical examination, chest x-ray and sputum cultures are done to check for active disease. Symptoms include cough, night sweats, tiredness, chills, loss of appetite, weight loss and chest pain.