A latent (inactive) tuberculosis (TB) infection is the
presence of TB bacteria in a person's lungs even though he or she does not have
symptoms of TB (such as coughing, weight loss, fatigue, or fever).
A person with latent tuberculosis infection has no signs of active TB on
a chest X-ray, and no TB-causing bacteria can be found in the mucus from the
person's lungs (sputum). The only proof that the person has a TB infection is a
positive TB skin test or TB blood test (interferon-gamma release assay or IGRA).
People who have a latent TB
infection do not spread the disease to other people. They may need to take
medicine to prevent the bacteria from becoming active in the future.
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