1. National Center for AIDS/STD Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing 100050, PR China.
2. School of Public Health, University of California at Los Angeles, Los Angeles, CA 90095, USA.
3. Division of AIDS, Department of Disease Prevention and Control, Ministry of Health, Beijing, 100044, PR China.
4. Centre for Human Genetics, Edith Cowan University, Joondalup, Perth, WA 6207, Australia.