H7N9 is a subtype of avian influenza. The outer wax of influenza virus particles is covered by two types of surface glycoproteins, one type is phytohemagglutinin and one type is neuraminidase. H is further divided into 15 subtypes and N is divided into 9 subtypes. All human influenza viruses can cause avian influenza, but not all avian influenza viruses can cause human influenza, avian influenza viruses, H5, H7, H9 can be transmitted to humans, of which H5 is highly pathogenic. According to the characteristics of the influenza virus can be divided into HxNx a total of 135 subtypes, H7N9 subtype of avian influenza virus is one of them, only found in the past between the birds, no human infection has been found. The biological characteristics, pathogenicity, and transmission of this virus have not been analyzed on the basis of judgment so far.