What is latent tuberculosis?
“Latent tuberculosis” is the term used for people who test positive for tuberculosis (most commonly with a positive tuberculin skin test), but do not have any evidence of active infection. Currently one in three people worldwide are felt to harbor tuberculosis bacilli. Tuberculosis is transmitted through airborne spread of Mycobacterium tuberculosis. When a person with active pulmonary TB coughs, aerosolized droplets containing bacilli can invade the lungs of close contacts. In 90-95% of cases, the infected person’s immune system halts growth of the bacteria and active disease does not develop, although skin or serological testing for TB will convert to positive. Once positive, a person’s TB test will generally remain positive for life. Approximately one in ten latent infections will later progress to active disease unless treatment is given. Most cases of active tuberculosis result from reactivation of latent TB.
