School of Public Health, Peking University, Beijing 100191, China;
Center for Disease Control and Prevention, Beijing 102206, China;
National Center for AIDS/STD Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing 102206, China;
National Center for AIDS/STD Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing 102206, China;
School of Public Health, Peking University, Beijing 100191, China;
National Center for AIDS/STD Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing 102206, China;
School of Public Health, Peking University, Beijing 100191, China;
School of Public Health, Peking University, Beijing 100191, China;