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

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

Wanying Sun  1 , Ka Tim Choy  1 , Ka Man Cheng  1 , Christopher J Brackman  2 , Samuel Ms Cheng  1 , Thomas Hc Sit  2 , Anne Cn Tse  2 , Leslie D Sims  3 , Haogao Gu  1 , Amy Wy Tang  1 , Andrew Nc Wong  1 , Andrew Tl Tsang  1 , Joe Ct Koo  1 , Leo Lh Luk  1 , Hui-Ling Yen  1 , Malik Peris  1   4   5   6 , Leo Lm Poon  1   4   5   6
Affiliations

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

Wanying Sun et al. Euro Surveill. 2025 Jan.

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.

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Conflict of interest statement

Conflict of interest: None declared.

Figures

Figure
Figure
Phylogenetic trees of H5, N8 and N1 sequences from highly pathogenic avian influenza viruses isolated from Asia, North America, Europe and Africa, 2017–2024 (n = 261)
See this image and copyright information in PMC

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