1 Shaoxing Center for Disease Control and Prevention, Shaoxing, Zhejiang Province, China.
2 Shaoxing County Center for Disease Control and Prevention, Shaoxing, Zhejiang Province, China.
3 Shaoxing Center for Disease Control and Prevention Shaoxing, Zhejiang Province, China; Chinese Field Epidemiology Training Program, Beijing, China. Electronic address: [email protected].