Tuberculosis (TB) is infection with Mycobacterium tuberculosis, a type of bacterium. Tuberculosis infection typically occurs after repeated or prolonged exposure to the coughing of an actively infected person. Persons with HIV infection are at particularly high risk. Infection can involve any organ in the body, but the lungs are the most common site of damage. In active infection, there is damage to organs. In latent infection, the person carries the bacteria but does not have current signs of active infection. Latent TB infection is important to diagnose and treat because it can become active infection. Multidrug-resistant TB is resistant to (cannot be killed by) standard antibiotics. This type of TB arises from improper or incomplete treatment of TB infection or through exposure to a person infected with this type of bacterium. The July 23/30, 2008, issue of JAMA includes 2 articles about tuberculosis. This Patient Page is based on one previously published in the June 8, 2005, issue of JAMA.