1. Beijing Friendship Hospital, Capital Medical University, Beijing 100050, China
2. National Center for AIDS/STD Control and Prevention, Chinese Center for Disease Control and Prevention, 155 Changbai Road, Changping District, Beijing 102206, China
3. Chongqing Center for Disease Control and Prevention, Chongqing 400042, China
4. Department of Preventive Medicine, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
5. San Francisco Department of Public Health, San Francisco, CA 94102, USA
6. Department of Epidemiology and Biostatistics, University of California, San Francisco, CA 94105, USA
7. State Key Laboratory for Infectious Disease Prevention and Control, National Center for AIDS/STD Control and Prevention, Chinese Center for Disease Control and Prevention, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Beijing 102206, China
8. Shandong University School of Public Health, Jinan 250012, China