1. Shandong Center for Disease Control and Prevention, 16992 City Ten Road, Jinan 250014, Shandong, P.R. China
2. TEDA Institute of Biological Sciences and Biotechnology, Nankai University, 23 Hongda Street, TEDA, Tianjin 300457, P.R. China
3. Disease Prevention and Control Center of Ganzhou District, 27 Xianfu Street, Ganzhou District, Zhangye City, Gansu Province, P.R. China