| FAQ - Diseases and Disease Agents - Archived Through 2012
How long is the incubation time for tuberculosis (TB)?
According to the Centers for Disease Control and Prevention (CDC), "Usually within 2-10 weeks after initial infection with M. tuberculosis, the immune response limits further multiplication and spread of the tubercle bacilli; however, some of the bacilli remain dormant and viable for many years. This condition is referred to as latent TB infection. Persons with latent TB infection usually have positive purified protein derivative (PPD)-tuberculin skin-test results, but they do not have symptoms of active TB, and they are not infectious.”(1) About 10% of individuals with latent TB infection will develop active disease at some later point in life.
(1) CDC. Guidelines for Preventing the Transmission of Mycobacterium tuberculosis in Health-Care Facilities, 1994. MMWR Morbid Mortal Weekly Rep 1994;43(RR13), 1-132. Available at http://www.cdc.gov/mmwr//preview/mmwrhtml/00035909.htm