北京市高层次卫生技术人才培养计划2013-3-099;国家“十二五”科技重大专项2012ZX10004215-003-001This work was supported by grants from the Project of Beijing High-Level Technical Personnel Training in Health2013-3-099;National Science and Technology Support Projects for the“Twelfth Five-Year Plan”for Infectious Diseases of China2012ZX10004215-003-001