Department of Epidemiology;
Southern Medical College;
Guangzhou 510515;
Guangdong Province;
China;
Department of Genetics;
Institute of Epidemiology and Microbiology;
Chinese Center for Disease Control and Prevention;
Beijing 102206;
China;
Department of Infectious Diseases;
Nanfang Hospital;
Southem Medical College;
Guangzhou 510515;
Guangdong Province;
China;