TB incidence in the United States decreased during the past decade, largely as a result of more intensive TB control efforts. Nevertheless, TB control remains a public health priority for correctional systems, since TB outbreaks continue to occur in U.S. jails and prisons. Furthermore, a significant proportion of TB cases in the U.S. occur among persons who are over-represented in certain jails or prisons, including racial/ethnic minority populations, persons with human immunodeficiency virus (HIV) infection, and persons born in foreign countries that have high rates of TB. M. tuberculosis, the organism that causes TB, is transmitted through airborne respiratory droplets when an individual with active pulmonary TB coughs, sneezes, speaks, or sings. Transmission of M. tuberculosis depends on the length of time and frequency of the exposure, the degree of contagiousness of the infected person, the environment and airflow in which the exposure occurred, and the intensity of the contact with the TB organism itself. Infection with M. tuberculosis usually requires prolonged contact with an infectious case in an enclosed space. The majority of persons who become infected never develop active TB.