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TB, or tuberculosis, is caused by a bacterium called Mycobacterium tuberculosis. TB can attack any part of the body but usually attacks the lungs. TB disease was once a leading cause of death in the United States. Worldwide, TB still causes more deaths than any other infectious disease.

TB is spread through the air from one person to another. The bacteria are spread when a person with TB disease of the lungs or throat coughs or sneezes. People nearby can breathe in the TB germ and become infected.

People who are infected with TB (latent TB infection) have TB germs in their bodies but do not feel sick or have symptoms. They cannot spread TB. However, they may develop TB disease at some time in the future. Signs of TB disease include cough, fatigue, fever, coughing up blood, night sweats, and weight loss.

People with TB disease can be treated and cured if they seek medical help. Even better, people who have only TB infection can take preventive medication to reduce their risk of developing TB disease in the future.

Some differences between latent and active TB:

Latent TB Infection

Active TB Disease

TB germs are dormant (asleep) in your body. This phase can last for a long time.

TB germs are reproducing and spreading in your body.

You don't look or feel sick. Your chest x-ray usually is normal.

You usually feel sick. Typical symptoms include: a cough for longer than 3 weeks, weight loss, night sweats, and fever. A chest x-ray and other tests are needed to diagnose TB disease.

You can't spread TB to other people.

If the TB germs are in your lungs, you may spread TB to other people by coughing, sneezing, talking, or singing.