Cocirculation of Genetically Distinct Highly Pathogenic Avian Influenza H5N5 and H5N1 Viruses in Crows, Hokkaido, Japan

Abstract

We isolated highly pathogenic avian influenza (HPAI) H5N5 and H5N1 viruses from crows in Hokkaido, Japan, during winter 2023-24. They shared genetic similarity with HPAI H5N5 viruses from northern Europe but differed from those in Asia. Continuous monitoring and rapid information sharing between countries are needed to prevent HPAI virus transmission.

Keywords: H5N1; H5N5; Japan; crows; highly pathogenic avian influenza virus; influenza; respiratory infections; subtype; viruses; zoonoses.

Figure

Phylogenetic analysis of genetically distinct highly pathogenic avian influenza H5N5 and H5N1 viruses isolated in Japan in winter 2023–24. H5 hemagglutinin (A) and N5 neuraminidase (B) gene segments of H5N5 highly pathogenic avian influenza viruses (HPAIVs) isolated in winter 2023–24 were compared with reference strains within clade 2.3.4.4b obtained from GISAID (https://www.gisaid.org). Squares indicate H5N1 and circles indicate H5N5 HPAIVs isolated from crows in Hokkaido in winter 2023–24. Bold text indicates the H5N5 HPAIV isolated from a peregrine falcon in Kumamato in the southern part of Japan in winter 2023–24. Trees were constructed by using the maximum-likelihood method and MEGA 7 software (https://www.megasoftware.net). Bootstrap values (>50%) from 1,000 replicates are indicated on nodes. Isolated viruses belonging to subgroups G1, G2a, and G2d and clade 2.3.4.4b are indicated. Dates after strain names indicate sample collection dates for HPAIV-infected animals. Scale bar indicates number of nucleotide substitutions per site.