Tuberculosis

Tuberculosis is an infectious disease caused by strains of mycobacteria, mainly Mycobacterium tuberculosis, resulting in an estimated two million deaths each year worldwide, more than from any other single bacterial pathogen. Inhalation is the predominant pathway of infection, making pulmonary tuberculosis the most common form of tuberculosis. Tuberculosis may arise either from a recent infection with M. tuberculosis, or from the reactivation of dormant bacilli, years or decades after initial infection. Extrapulmonary tuberculosis mainly results from reactivation of a tuberculous focus after hematogenous dissemination or lymphogenous spread from a primary, usually pulmonary focus.