1. Sichuan Center for Disease Control and Prevention, Chengdu, Sichuan, China.
2. State Key Laboratory for Infectious Disease Prevention and Control, Key Laboratory for Medical Virology, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China.
3. Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Hangzhou, China.
4. Washington University, St. Louis, Missouri.