1. National Institute for Communicable Disease Control and Prevention, Beijing, People's Republic of China;
2. State Key Laboratory of Infectious Diseases Prevention and Control, Beijing, People's Republic of China;
3. Sichuan Provincial Center for Disease Control and Prevention, Chengdu, People's Republic of China;
4. Université de Montréal, Montreal, Quebec, Canada;
5. Guangxi Provincial Center for Disease Control and Prevention, Nanning, People's Republic of China;
6. Guangdong Provincial Center for Disease Control and Prevention, Guangzhou, People's Republic of China;
7. Jiangxi Provincial Center for Disease Control and Prevention, Nanchang, People's Republic of China;
8. Jiangsu Provincial Center for Disease Control and Prevention, Nanjing, People's Republic of China;
9. Guizhou Provincial Center for Disease Control and Prevention, Guiyang, People's Republic of China