1. Yangfeng Wu, Aoming Jin, Gaoqiang Xie, and Guang Jia are with the Peking University Clinical Research Institute, Beijing, China. Lei Wang and Jianguo Xu are with the State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing. Kaitai Liu is with the National Institute for Nutrition and Food Safety, Chinese Center for Disease Control and Prevention, Beijing. Xiaofeng Liang...