1. National Institute for Viral Disease Control and Prevention, China CDC, Beijing, People's Republic of China
2. Peking Union Medical College, Beijing, People's Republic of China
3. Centers for Disease Control and Prevention, Atlanta, Georgia
4. Centers for Disease Control and Prevention, Jinan City, Shandong Province, People's Republic of China
5. Centers for Disease Control and Prevention, Zhengzhou City, Henan Province, People's Republic of China
6. Centers for Disease Control and Prevention, Hefei City, Anhui Province, People's Republic of China