Abstract:Objective To investigate the molecular genetic characteristics of the first human case infected with the avian influenza virus H5N1 clade 2.3.4.4b in eastern China. Methods Patient′s sputum and bronchoalveolar lavage fluid(BALF) specimens were collected for virus identification using real-time reverse-transcription PCR(RT-PCR)assay, virus culture and sequencing.The virus evolution and origin were investigated using phylogenetic analysiswith the software Mega 6.1. Results An influenza A virus isolate was obtained from the BALF specimens of a case with severe respiratory syndromes, which belonged to influenza virus H5N1 clade 2.3.4.4b.Whole-genome sequencing of the virus isolate showed that the 8 genome fragment shared high nucleotide sequence homology(99.1% to 99.7%) with H5N1 isolates that had been prevalent in Eurasia since 2021,notably in southern China.No mutation was identified in 226 to 228 amino acids in the HA protein of the virus, and the binding ability of avian receptor alpha-2,3 galactoside sialic acid(SAα2,3Gal) was reserved, which was characterized as highly pathogenic avian influenza H5N1 virus.No mutationassociated with resistance to oseltamivir, zanamivir or adamantane was detected in NA or M2 protein, and no mutations were identified in E627K or D701N sites of JS210 or PB2 protein, or D92E site of NS1 protein, indicating limited adaptability of this virus isolate to humans. Conclusions The avian influenza virus H5N1 clade 2.3.4.4b may spillover avian to humans and cause severe diseases.Persistent intensified surveillance of avian influenza viruses is required.


A/Jiangsu/NJ210/2023(H5N1): EPI1868382~EPI1868389