<s>[INST] What is latent TB infection? [/INST] 
In most people who breathe in TB germs and become infected, the body is able to fight the TB germs to stop them from growing. The TB germs become inactive, but they remain alive in the body and can wake up and become active later. This is called latent TB infection, or LTBI for short.

People with LTBI

Have no symptoms.
Don’t feel sick.
Can’t spread TB germs to others.
Usually have a positive TB blood test or positive skin test reaction.
May develop TB disease if they do not receive treatment for LTBI.
People with LTBI do not have symptoms, and they cannot spread TB germs to others. However, if latent TB germs become active in the body and multiply, the person will go from having LTBI to being sick with TB disease. For this reason, people with LTBI should be treated to prevent them from developing TB disease. Treatment of LTBI is essential to controlling TB in the United States because it substantially reduces the risk that LTBI will progress to TB disease.
 Source: CDC. Link: https://www.cdc.gov/tb/publications/faqs/tb-qa.htm. Field: Lung Disease. Disease: Tuberculosis </s>