Avoid getting active TB

Active tuberculosis (TB) is an infection that is spreading in a person's body, and it is very contagious.

The World Health Organization (WHO) estimates that one-third of the world's population is infected with the bacteria that causes TB. To avoid getting an active TB infection:

• Do not spend long periods of time in stuffy, enclosed rooms with anyone who has active TB until that person has been treated for at least 2 weeks.
• Use protective measures, such as face masks, if you work in a facility that cares for people who have untreated TB.
• If you live with someone who has active TB, help and encourage the person to follow treatment instructions.

Prevent latent TB from becoming active

Usually, treatment with isoniazid for about 9 months or rifampin for 4 months can prevent a latent TB infection from developing into active TB. Treatment is recommended for anyone with a skin test that shows a TB infection, and is especially important for people who:

• Are known to or are likely to be infected with the human immunodeficiency virus (HIV).
• Have close contact with a person who has active TB.
• Have a chest X-ray that suggests a TB infection, and have not had a complete course of treatment.
• Inject illegal drugs.
• Have a medical condition or take medications that weaken the immune system.
• Have had a tuberculin skin test within the past 2 years that did not show a TB infection but now a new test indicates an infection.

Can the TB vaccine help?

A TB vaccine (bacille Calmette-Guerin, or BCG) is used in many countries to prevent TB. However, this vaccination is almost never used in the United States because:

• The risk of getting TB is low in the U.S.
• The vaccine is not effective in adults who receive it.
• The BCG vaccine may cause a tuberculin skin test to indicate a TB infection even if a person is not infected with TB. This complicates the use of the tuberculin skin test to check people for TB.