1. Department of Microbiology & Infectious Disease Center, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, People's Republic of China
2. Jiangsu Provincial Center for Disease Control and Prevention, Nanjing, People's Republic of China
3. Zhengzhou Municipal Center for Disease Control and Prevention, Zhengzhou, People's Republic of China
4. Beijing Youan Hospital, Capital Medical University, Beijing, People's Republic of China