[1] Sun Yat Sen Univ, Dept Med Stat & Epidemiol, Sch Publ Hlth, Guangzhou, Guangdong, Peoples R China
[2] Guangzhou Ctr Dis Control & Prevent, Guangzhou, Guangdong, Peoples R China
[3] Massachusetts Gen Hosp, Infect Dis Unit, Boston, MA 02114 USA
[4] Univ Wisconsin, Sch Med & Publ Hlth, Madison, WI USA