1. School of Public Health, Qingdao University, Qingdao, China.
2. State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China.
3. Shanxi Province Center for Disease Control and Prevention, Taiyuan, China.
4. Wuxiang County Center for Disease Control and Prevention, Wuxiang, China.
5. School of Basic Medicine, Qingdao University, Qingdao, China.