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Tuberculosis (TB)

TB, or tuberculosis, is a disease caused by a bacteria named M. tuberculosis. This bacteria can infect any part of the body, but it most commonly affects the lungs. TB is spread through the air from one infected person to another.

There are two types, or stages, of TB. The first is latent, or inactive, TB. In latent TB, there are live TB bacteria inside a person, but that person is not sick. Someone with latent TB feels fine: no cough, no fever. Someone with latent TB cannot spread this infection.

About 10% of people with latent TB will progress to active TB. People with active TB are sick. They most commonly have cough and fever. People with active TB can spread this infection to other people. Active TB is a very serious, even life-threatening illness. In most of the world TB is common.

Because of the risk of latent TB progressing to active TB, doctors recommend that people with latent TB take a medication for several months. This medication reduces the chance of progression from latent to active TB. Most commonly this medicine is INH (isoniazid).


People with latent TB:

  • feel normal
  • can't spread this sickness
  • usually have a positive skin test

People with active TB

  • usually feel sick (cough for more than 3 weeks, fever, weight loss, chills)
  • can spread this illness to others
  • usually have a positive skin test
  • may have an abnormal chest x-ray

If you were born outside of the United States and have never had a skin test for TB, the University of Washington advises that you get one.

If you have symptoms that are similar to those of active tuberculosis (for example, cough for more than three weeks), you should make an appointment to be seen by a doctor. Contact the Hall Health Patient Service Center for an appointment.

For more information

An excellent source of information on tuberculosis is the Center for Disease Control. Their fact sheet on latent TB is very informative.