Tuberculosis

diagnosis and treatment. However, given that most deaths from TB are preventable, the death toll from the disease is still unacceptably high and efforts to combat it must be accelerated. Worldwide the proportion of new cases with multidrug-resistant TB (MDR-TB) was 3.5 in 2013 and has not changed compared with recent years. However, much higher levels of resistance and poor treatment outcomes are of major concern in some parts of the world. Of the estimated 9 million people who developed TB in 2013, more than half (56) were in the South-East Asia and Western Pacific Regions. A further one quarter were in the African Region, which also had the highest rates of cases and deaths relative to population. India and China alone accounted for 24 and 11 of total cases, respectively. Definition Pulmonary tuberculosis is an infectious disease caused by Mycobacterium tuberculosis. In many cases, M tuberculosis becomes dormant before it progresses to active TB. It most commonly involves the lungs and is communicable in this form, but may affect almost any organ system including the lymph nodes, CNS, liver, bones, genitourinary tract, and gastrointestinal tract. Etiology The development of TB requires infection by M tuberculosis and inadequate containment by the immune system. Patients infected with M tuberculosis who have no clinical, bacteriologic, or radiographic evidence of active TB are said to have latent TB infection. Active TB may occur from reactivation of previously latent infection or from progression of primary infection. Transmission of TB occurs from individuals infected with pulmonary (and rarely laryngeal) disease. Infection results from the inhalation of aerosolized droplets containing the bacterium. The likelihood of transmission depends on the infectivity of the source case, the degree of exposure to the case (proximity, ventilation, and the length of exposure), and susceptibility of the person in contact with an infected case. HIV-infected individuals are