[Skip to Navigation]
Sign In
JAMA Patient Page
March 6, 2013


JAMA. 2013;309(9):938. doi:10.1001/2012.jama.10804

Tuberculosis (TB) is a communicable infection (can be transmitted from person to person) that usually affects the lungs. It is spread by airborne droplets when an infected person coughs or sneezes. It is caused by a bacterium called Mycobacterium tuberculosis. At the time of diagnosis, people with TB usually have a variety of symptoms such as low-grade fever, constant cough with sputum (phlegm), night sweats, and unintentional weight loss.

Classifying tb

  • Active TB describes an ongoing infection in which a person develops symptoms and has a positive (abnormal) result on a test for TB.

  • Latent TB occurs when a person with no symptoms has a positive result on a TB skin or blood test. This suggests that the person was infected with TB in the past but the bacteria are in a dormant or inactive state. Persons with latent TB cannot spread the TB bacteria to others.

  • Multidrug-resistant TB (MDR-TB) is a form of active TB caused by bacteria that do not respond to the medications most commonly used to treat TB.

Risk factors for tb

  • A deficient or weakened immune system, such as in people with diabetes or HIV/AIDS

  • Traveling to or living in countries where tuberculosis is endemic (found commonly)

  • Working in health care or refugee camps

  • Living in overcrowded and poorly ventilated residences

Evaluation for suspected tb

  • Tuberculin skin test (also called PPD, or purified protein derivative). In response to this injection, if a person has been infected with TB, immune cells will indurate (harden) the area surrounding the injection site. The area of induration is measured 48 to 72 hours after injection and used to determine the likelihood of TB infection.

  • Chest x-ray may be done to distinguish between active and latent TB.

  • A blood test may be done to check for cytokines (substances released by immune cells) that are unique to TB infections.


  • Several antimicrobials (medicines that kill microorganisms or interfere with their growth) are used to treat tuberculosis.

  • Treatment usually lasts for 6 months and requires close monitoring by an infectious diseases specialist or other specialist.

  • Complete treatment of a person with any form of TB is essential to maintain the person's health and to prevent the spread of tuberculosis to others.


  • In high-risk health care settings, appropriate precautions should be followed. This includes wearing masks specifically designed to prevent the spread of TB.

  • Patients diagnosed as having latent TB may be given medications to kill dormant bacteria and prevent the development of active TB.

  • In countries where TB is endemic, people may be given bacille Calmette-Guérin (BCG), a vaccine against TB.

For more information

Inform yourself

To find this and previous JAMA Patient Pages, go to the Patient Page link on JAMA 's website at www.jama.com. Many are available in English and Spanish.

Source: US Centers for Disease Control and Prevention

The JAMA Patient Page is a public service of JAMA. The information and recommendations appearing on this page are appropriate in most instances, but they are not a substitute for medical diagnosis. For specific information concerning your personal medical condition, JAMA suggests that you consult your physician. This page may be photocopied noncommercially by physicians and other health care professionals to share with patients. To purchase bulk reprints, call 312/464-0776.