1. Key Laboratory for Medical Virology, Ministry of Health, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention, No. 155, Changbai Road, Changping District, Beijing 102206, China
2. National Institute for Nutrition and Food Safety, Chinese Center for Disease Control and Prevention, Beijing 100050, China
3. Hebei Center for Disease Control and Prevention, No. 241, Qingyuan Street, Yuhua District, Shijiazhuang 050000, China