Not everyone who is infected with the tuberculosis bacterium gets sick. Therefore, there are two conditions associated with tuberculosis: latent tuberculosis infection and tuberculosis disease.

Latent tuberculosis infection

Tuberculosis bacteria can survive in the body without causing disease. This is called latent TB infection. For most people who inhale TB bacteria and become infected, the body is able to fight the bacteria and stop them from growing.

People with latent TB infection:

• Have no symptoms

• Do not feel uncomfortable

• Cannot spread TB bacteria to others

• Usually have a positive TB skin test reaction or a positive TB blood test

• May develop TB if not treated for latent TB infection

  
  

Many people with latent TB infection never develop TB disease. In these people, the TB bacteria are inactive for life and do not cause disease. But in others, especially those with weakened immune systems, the bacteria can become active, multiply, and cause TB disease.

TB Disease

If the immune system cannot stop the growth of TB bacteria, they become active. When TB bacteria are active (multiply in your body), this is called TB disease. People who have TB can get sick. They may also spread the bacteria to the people they are with every day.

Many people with latent TB infection never develop TB disease. Some people are infected with TB soon after (within a few weeks) and their immune systems are not yet capable of fighting the TB bacteria. Others may get sick years later because their immune systems become weak for other reasons.

People with weakened immune systems, especially those with HIV, are at much higher risk of developing TB than people with normal immune systems.

There are two tests used to detect TB bacteria in the body: the tuberculosis skin test (TST) and the TB blood test. A positive TB skin test or TB blood test only indicates that a person is infected with TB bacteria. It cannot tell if a person has latent TB infection (LTBI) or has developed TB disease. Other tests, such as a chest x-ray and sputum sample, are also needed to determine if a person has TB.