The Importance of Exogenous Reinfection in the Tuberculosis Endemic of Taiwan

Tuberculosis (TB) remains the most important infectious disease in the world. In Taiwan, the incidence of TB increased in recent years. The failure of control implies the necessity to reevaluate the epidemiology of Mycobacterium tuberculosis. It is widely thought that most cases of TB are caused by reactivation of a latent infection. Treatment programs have therefore focused on cure rates rather than tracking of additional cases. But recent studies showed that exogenous reinfection plays an important role in the development of TB. In addition, it seems that the higher the local incidence, the more important exogenous reinfection is. The question of exogenous reinfection versus endogenous reactivation has an impact on the distribution of resources for the prevention and treatment of TB. Based on these evidences, we hypothesize that exogenous reinfection is very important in the Taiwan endemic. Therefore, we design a series of studies to evaluate the individual contribution of exogenous reinfection and endogenous reactivation in the Taiwan endemic, and to realize the impact of exogenous reinfection. First, we will identify the patients with TB relapse after complete treatment. The M. tuberculosis isolates responsible for their initial and recurrent episodes will then be genotyped to clarify the percentage of exogenous reinfection and endogenous reinfection.