To analyze the traceability and genetic characteristics of a highly pathogenic H7N9 avian influenza virus strain isolated in Nanning city, 2017 through sequencing of HA and NA gene of the virus. Both HA and NA gene sequences of the isolated virus were amplified with RT-PCR and seque3nced with BLAST database of NCBI. The phylogenic tree analysis was drawn with Mega5.1 and variations in dominant loci for proteins were statistically analyzed. The established phylogenetic tree showed that the HA and NA gene sequences of the cirus were mainly divided into two branches of Yangtze River Delta and Peral River Delta; the HA and NA gene of the isolated A/Nanning/01/2017(H7N9) virus were evolved from the Peral River Delta Branch and were highly homologous with those of the avian influenza H7N9 virus isolated in Guangdong province. The inserted 4 amino acids at HA protein cleavage site mutated from PEIPKGR GLF to PEVPKRKRTAR GLF; the mutation involved in 5 basic amino acids and resulted in molecular characteristics of high pathogenicity of avian influenza virus.

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