[1] Sichuan Univ, West China Hosp, Ctr Clin Epidemiol & Evidence Based Med, Chengdu 610041, Peoples R China
[2] Sichuan Univ, West China Sch Publ Hlth, Dept Epidemiol & Biostat, Chengdu 610041, Peoples R China
[3] Univ London London Sch Hyg & Trop Med, Dept Global Hlth & Dev, London WC1H 9SH, England
[4] Univ London London Sch Hyg & Trop Med, Dept Hlth Serv Res & Policy, London WC1H 9SH, England
[5] Chinese Ctr Dis Control & Prevent, Div Infect Dis, Key Lab Surveillance & Early Warning Infect Dis, Beijing 102206, Peoples R China
[6] Univ London London Sch Hyg & Trop Med, Dept Infect Dis Epidemiol, London WC1E 7HT, England