[Reinfection of tuberculosis in HIV-negative persons].

To clarify our knowledge about exogenous reinfection of Mycobacterium tuberculosis in HIV-negative persons, we review the literatures on this issue as much as possible, and we deduce the following; 1) Risk of exogenous reinfection may be not rare in itself, but quantifiably determined by host factor, bacilli factor and intensity of exposure. 2) Generally, when already-infected persons are exposed to exogenous reinfection Mycobacterium tuberculosis, risk of disease due to the exposure is definitely lower than not-already-infected persons (estimated relative risk: 8.5%). But the protection rate can be similar with that of BCG vaccination under most favorable condition. 3) It cannot be concluded definitely that the tuberculosis disease in already-infected persons is almost always due to endogenous reactivation.