Chinese Field Epidemiology Training Program Chinese Center for Disease Control and Prevention Beijing 100050 China;
Chinese Field Epidemiology Training Program and Zhejiang Provincial Center for Disease Control and Prevention Huangzhou 310052 Zhejiang China;
Chinese Field Epidemiology Training Program and Chongqing Center for Disease Control and Prevention Chongqing 400042 China;
Chinese Field Epidemiology Training Program and Fujian ProvincialCenter for Disease Control and Prevention Fuzhou 350001 Fujian China;