[1] Weifang Yidu Cent Hosp, Weifang City 262500, Shandong Provin, Peoples R China
[2] Chinese Ctr Dis Control & Prevent, Natl Inst Communicable Dis Control & Prevent, Changping Liuzi 5, Beijing 102206, Peoples R China
[3] Capital Med Univ, Yanjing Med Coll, Beijing City 101300, Peoples R China