浙江省一起野鸟H5N6亚型高致病性禽流感疫情的流行病学调查OA

In June 2024,an outbreak of H5N6 subtype highly pathogenic avian influenza(H5N6 HPAI)occurred in wild birds in the Xiangshan Sea area of Ningbo City,Zhejiang Province.A systematic epidemiological investigation and pathogen genetic analysis were conducted to identify the prevalence and variation of the strain of wild bird virus.The epidemiological investigation revealed that the qualification rate of H5 subtype avian influenza(AI)immunization antibodies in domestic waterfowl on farms around the infected holding reached 93％,and all results of nucleic acid tests were negative.Virus isolation and gene sequencing identified that the HA gene of the isolated virus was 99％ identical to A/crow/Miyagi/TU69-55/2023(H5N1),and 95％ to Re-14 vaccine strain,falling into 2.3.4.4b clade;the HA protein cleavage site was characterized by high pathogenicity due to its consecutive basic amino acids,T156A mutation available in the HA protein might enhance its binding affinity to human receptors;the NA gene was 99％ identical to A/Guangdong/1/2021(H5N6),and no deletion of amino acids was observed in the neck region of the NA protein.Phylogenetic analysis indicated that the strain was highly homologous to H5N1 subtype strain isolated from Japan and H5N6 subtype strain from China,indicating possible introduction via migratory birds.In conclusion,wild birds were recommended to be continuously monitored to prevent possible transmission to domestic poultry,although current vaccines were effective for poultry,reducing the risk of outbreak spread.