Detection and characterisation of high pathogenicity avian influenza virus (H5N1/H5N8) clade 2.3.4.4b, Hong Kong SAR, China, 2021 to 2024

Euro Surveill. 2025 Jan;30(1):2400839. doi: 10.2807/1560-7917.ES.2025.30.1.2400839.

Abstract

We isolated three genotypes of highly pathogenic avian influenza virus (HPAIV) clade 2.3.4.4b from wild birds infected with H5N1 (n = 12) and H5N8 (n = 1) in Hong Kong SAR 2021-2024. Viruses from two spoonbills from late 2022 were genetically related to a virus from a human in China. Four tested viruses exhibited variable virulence in mice but were susceptible to approved antivirals. No neutralising antibody was detected in 63 age-stratified human sera, suggesting potential risk should the virus adapt to humans.

Keywords: Avian influenza virus; H5N1; H5N8; surveillance and risk assessment.

MeSH terms

  • Animals
  • Animals, Wild / virology
  • Antibodies, Neutralizing / blood
  • Antiviral Agents / pharmacology
  • Antiviral Agents / therapeutic use
  • Birds* / virology
  • China / epidemiology
  • Genotype
  • Hong Kong / epidemiology
  • Humans
  • Influenza A Virus, H5N1 Subtype* / genetics
  • Influenza A Virus, H5N1 Subtype* / isolation & purification
  • Influenza A Virus, H5N1 Subtype* / pathogenicity
  • Influenza A Virus, H5N8 Subtype* / genetics
  • Influenza A Virus, H5N8 Subtype* / isolation & purification
  • Influenza A Virus, H5N8 Subtype* / pathogenicity
  • Influenza in Birds* / epidemiology
  • Influenza in Birds* / virology
  • Influenza, Human* / epidemiology
  • Influenza, Human* / virology
  • Mice
  • Phylogeny
  • Virulence

Substances

  • Antibodies, Neutralizing
  • Antiviral Agents