1. Epidemiology & Biostatistics, School of Public Health, Jilin University, Changchun, Jilin Province 130021
2. National Center for AIDS/STDs Control & Prevention, Chinese Center for Disease Control & Prevention, Beijing 102206
3. Health Management, The First Hospital of Jilin University, Changchun, Jilin Province 130021, China
4. Community Health & Epidemiology, College of Medicine, University of Saskatchewan, 107 Wiggins Road, Saskatoon, CanadaS7N 5E5
5. Kaiyuan Center for Disease Control & Prevention, Kaiyuan, Yunnan Province 661600, China