Tuberculosis (TB) is an infectious disease caused by a bacteria that causes fever, cough, and wasting. It usually progresses slowly and is eventually fatal, but can be cured with antibiotic treatment. There is a long latent period after infection before symptoms appear. A tuberculin skin test is used to determine if someone is infected.
For most travelers, the risk of TB infection is low. However, for those who are planning long-term travel in a country where TB is prevalent, a skin test is a good idea. Other high-risk situations include routinely extended contact with people in healthcare facilities, prisons or homeless shelter populations, as TB is prevalent in these groups. People who were born overseas and are returning for a visit may need testing before traveling. A person that has had a tuberculosis vaccine called BCG that is used in many countries, may have an inaccurate TB test reading.
The nurse will inject a small amount of liquid under the skin of the arm. The liquid contains an extract of the bacteria that causes TB (it cannot cause a TB infection). A person who is healthy will not have a reaction to the skin test; a person who is infected with TB will react to the skin test. A positive skin test means you have been infected with the tuberculosis bacteria. A positive TB test, plus a negative chest x-ray and exam by a doctor means that you have latent (not contagious) TB. You may be offered medication to prevent active (contagious) TB.
A two-step TB skin test is recommended for those who people that have had repeated tuberculin skin tests in their life and have high-risk of exposure to tuberculosis. A second TB skin test is administered one to three weeks after the first test. Each test is read 48 to 72 hours after administration, so it is wise to allow at least four weeks for the testing process. People who plan an extended stay in high-risk areas may need to be tested more frequently.
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