Epidemiology of tuberculosis - ？？？？？？.ppt

?? ??????? ????? ??? Definition caused by bacteria belonging to the Mycobacterium tuberculosis complex usually affects the lungs Up to one-third of cases other organs are involved If properly treated ? curable If untreated ? fatal within 5 years in more than half of cases Etiologic agent M. tuberculosis a rod-shaped non-spore-forming thin aerobic bacterium measuring 0.5? by 3 ?. neutral on Gram’s staining cannot be decolorized by acid alcohol ? acid-fast bacilli (AFB) Epidemiology of tuberculosis 8 million new cases worldwide 1.6 million deaths from tuberculosis in 2007 The prevalence rate in Korea TB incidence rate in Korea (new case, notified) Infection of tuberculosis Transmitted by droplet nuclei Aerosolized by coughing, sneezing, speaking 10? droplet Suspended in the air for several hours Gain access to the terminal air passages Infectivity Cavitary lesions Endobronchial or laryngeal tuberculosis Contact intensity From Exposure to Infection Transmitted by droplet nuclei Aerosolized by coughing, sneezing, speaking Tiny droplets ; 10? droplet Suspended in the air for several hours Gain access to the terminal air passages Determinants of transmission probability of contact with a case of tuberculosis, intimacy and duration of that contact, degree of infectiousness of the case, shared environment of the contact The spread of infection Cavitary lesions Endobronchial or laryngeal tuberculosis sputa containing as many as 105 AFB/mL less infectious Patients with sputum smear (-), culture (+) noninfectious sputum culture (-) pulmonary disease extrapulmonary tuberculosis From Infection to Disease Depends largely on endogenous factors the individual’s innate susceptibility to disease level of function of cell-mediated immunity Risk factors for active tuberculosis Latent infection ??? ?? Disease Primary tuberculosis Clinical illness directly following infection Common among children(≤ 4yr) May be severe and disseminated Secondary tuberculosis Dormant bac