Bin Chen1, Qiyong Liu2. 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, Changping, Beijing, China; China CDC Key Laboratory of Surveillance and Early-Warning on Infectious Disease, Chinese Center for Disease Control and Prevention, Changping, Beijing, China; Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Hangzhou, China; Xiamen Entry-Exit Inspection and Quarantine Bureau, Xiamen, China. 2. State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Changping, Beijing, China; China CDC Key Laboratory of Surveillance and Early-Warning on Infectious Disease, Chinese Center for Disease Control and Prevention, Changping, Beijing, China; Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Hangzhou, China. Electronic address: liuqiyong@icdc.cn.