[1] Chinese Acad Inspect & Quarantine, Inst Hlth Quarantine, Beijing 100123, Peoples R China
[2] Chongqing Med Univ, Childrens Hosp, Dept Diarrhea, Chongqing 400014, Peoples R China
[3] Shandong Univ, Dept Epidemiol & Hlth Stat, Jinan 250012, Peoples R China
[4] Shandong Prov Dis Prevent & Control Ctr, Dept Infect Dis Control, Jinan 250001, Peoples R China
[5] Chinese Peoples Armed Police Forces, Ctr Dis Control & Prevent, Beijing 102613, Peoples R China
[6] Chinese Ctr Dis Control & Prevent, Natl Ctr Publ Hlth Surveillance & Informat Serv, Beijing 102206, Peoples R China