[1] Chinese Ctr Dis Control & Prevent, Natl Inst Viral Dis Control & Prevent, NHC Key Lab Med Virol & Viral Dis, Beijing 100052, Peoples R China
[2] Columbia Univ, Mailman Sch Publ Hlth, New York, NY 10032 USA
[3] Gansu Univ, Tradit Chinese Med Sch Publ Hlth, Lanzhou 730000, Peoples R China