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In most people who breathe in the bacteria and become infected, the body is able to fight the bacteria to stop them from growing. The bacteria become inactive, but they remain alive in the body and can become active later. This is called latent tuberculosis. People with this form of the disease:
- Have no symptoms of tuberculosis
- Don't feel sick
- Can't spread TB to others
- Usually have a positive TB skin test (PPD test) reaction.
Some people with the latent form of the disease can develop active tuberculosis disease if they do not receive treatment.
If the body's resistance is low because of aging, malnutrition, infections such as HIV, or other reasons, the bacteria may break out of hiding and cause active tuberculosis.
In these cases, symptoms can include:
- Unexplained weight loss
- Night sweats
- Weakness or fatigue
- Loss of appetite
- Cough that lasts 3 weeks or longer
- Pain in the chest
- Coughing up blood or sputum.
Specific tests will help the doctor make the diagnosis and determine whether it is the disease is active or latent (see Latent Versus Active Tuberculosis). These TB tests can include a TB skin test (PPD test), TB blood test, and other tests, such as a chest x-ray and samples of sputum.