Institution: | Author affiliations: People''s Liberation Army Institute of Disease Control and Prevention, Beijing, People''s Republic of China (W.-Y. Zhang, H.-L. Sun, S.-L. Li);;Beijing Institute of Microbiology and Epidemiology, Beijing (W.-Y. Zhang, J.-F. Jiang, W. Liu, W.-C. Cao);;Inner Mongolia Center for Disease Control and Prevention, Hohhot, People''s Republic of China (W.-D. Guo);;Chinese Center for Disease Control and Prevention, Beijing (S.-H. Sun) |