School of Public Health;
Peking Union Medical College;
Tsinghua University;
Beijing 100730;
China;
National Center for AIDS/STD Control and Prevention;
Beijing 102206;
China;
Tulane University Health Sciences Center;
School of Public Health and Tropical Medicine;
New Orleans;
LA;
USA;
Kaiyuan Center for Disease Control and Prevention;
Kaiyuan 661600;
Yunnan;
China;
University of North Carolina at Chapel Hill Chapel Hill NC;
USA;