1. State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China.
2. Zhejiang Provincial Center for Disease Control and Prevention, Hangzhou, China.
3. Liaoning Provincial Center for Disease Control and Prevention, Shenyang, China.
4. Shenzhen Entry-Exit Inspection and Quarantine, Shenzhen, China.