1. Department of Epidemiology and Health Statistics, School of Public Health, Southeast University, 87 Dingjiaqiao Avenue, Nanjing 210009, China
2. Jiangsu Provincial Medical Innovation Center, National Health Commission Key Laboratory of Enteric Pathogenic Microbiology, Jiangsu Provincial Center for Disease Control and Prevention, Nanjing 210009, China
3. Key Laboratory of Environmental Medicine Engineering, Ministry of Education, School of Public Health, Southeast University, Nanjing 210009, China
4. Department of Epidemiology, School of Public Health, Fudan University, Shanghai 200433, China