1. Department of Epidemiology and Health Statistics, Xiangya School of Public Health, Central South University, Changsha, China.
2. Hunan Children's Hospital, Medical Record Statistics and Library Management Office, Changsha, China.
3. Supervision Office, Tangshan Animal Health Inspection Institute, Tangshan, China.
4. Center for Preventive Medicine Experiment, Xiangya School of Public Health, Central South University, Changsha, China.