1. Department of Epidemiology and Health Statistics, College of Public Health, Zhengzhou University, Zhengzhou, P. R. China
2. School of Public Health and Tropical Medicine, Southern Medical University, Guangzhou, P. R. China
3. Department of Preventive Medicine, Shenzhen University School of Medicine, Shenzhen, P. R. China
4. Department of Prevention and Health Care, Military Hospital of Henan Province, Zhengzhou, P. R. China
5. Department of Blood Transfusion, Xijing Hospital, The Fourth Military Medical University, Xian, P. R. China
6. Department of Public Health Surveillance and Advisory, Zhejiang Provincial Centre for Disease Control and Prevention, Hangzhou, P. R. China