The reinfection with S. japonicum in residents with higher prevalence in island region, poyang lake,observed after selective treatment of positive cases had been taken since 1989. During 1989 ?

• 在洲岛型日本血吸虫病重疫区；采用阳性病人选择性化疗的防治措施后；1989一1992年居民血吸虫感染率分别为39.；6%25、25