When a person breathes in the TB bacteria, in most cases, the body is able to fight them to stop them from growing. The bacteria become inactive, but do not die. They lie latent, and can become active later. This state is called TB infection. People who are infected with TB do not feel sick, do not have any symptoms, and cannot spread the disease. But they could develop TB disease at some time in the future.
Frequently Asked Questions about Tuberculosis. (2013). [ebook] New Delhi-110002, India: Regional Office for South-East Asia, World Health Organization. Available at: http://www.searo.who.int/about/administration_structure/cds/ en/index.html [Accessed 1 Jan. 2018].