To comprehend the genetic evolutionary characteristics and biological properties of the H4N1 subtype avian influenza virus(AIV)in China,this study conducted whole genome sequen-cing,genetic evolutionary analysis,and pathogenicity test in BALB/c mice of a duck-derived H4N1 subtype AIV strain(DK/GX/E1424/20)isolated from the live poultry market in the southern re-gion in 2020.The results indicated that the cleavage site motif of the HA protein was PEKASR/GLF,which conformed to the characteristics of low pathogenic AIV.All the eight gene fragments were situated in the Eurasian lineage,and the homology of AIV-related genes of the H1N1,H3N8,H4N6,H6N1,and H10N8 subtypes isolated from wild waterfowl was the highest,representing a recombinant virus strain.Without prior adaptation,it replicated effectively in the lungs and turbi-nates of mice,with viral titers of 3.00 and 2.08 log10EID50/mL respectively,and induced weight loss in infected mice.This study suggested that this virus had significant genetic diversity and low pathogenicity in mice,posing a potential risk for mammalian infection.

To comprehend the genetic evolutionary characteristics and biological properties of the H4N1 subtype avian influenza virus(AIV)in China,this study conducted whole genome sequen-cing,genetic evolutionary analysis,and pathogenicity test in BALB/c mice of a duck-derived H4N1 subtype AIV strain(DK/GX/E1424/20)isolated from the live poultry market in the southern re-gion in 2020.The results indicated that the cleavage site motif of the HA protein was PEKASR/GLF,which conformed to the characteristics of low pathogenic AIV.All the eight gene fragments were situated in the Eurasian lineage,and the homology of AIV-related genes of the H1N1,H3N8,H4N6,H6N1,and H10N8 subtypes isolated from wild waterfowl was the highest,representing a recombinant virus strain.Without prior adaptation,it replicated effectively in the lungs and turbi-nates of mice,with viral titers of 3.00 and 2.08 log10EID50/mL respectively,and induced weight loss in infected mice.This study suggested that this virus had significant genetic diversity and low pathogenicity in mice,posing a potential risk for mammalian infection.