Tuberculosis is an airborne disease caused by the Mycobacterium tuberculosis (M. tuberculosis). M. tuberculosis and seven very closely related mycobacterium species (M. bovis, M. africanum, M. microti, M. caprae, M. pinnipedii, M. canetti, and M. mungi) together comprise what is known as the Mycobacterium tuberculosis complex. Most, but not all of these species have been found to cause disease in humans. Tuberculosis can affect any organ in the body. Pulmonary tuberculosis is the most frequent site of involvement; extrapulmonary tuberculosis is less frequent