Whole-genome sequencing of 37 H5 high pathogenicity avian influenza viruses isolated in Laos between 2019 and 2024 has revealed persistent viral circulation, extensive genetic diversity, and ongoing reassortment across multiple clades and genotypes.
High pathogenicity avian influenza viruses belonging to several H5 clades have caused outbreaks in Laos since 2004, with clade 2.3.2.1e H5N1 viruses predominating in the country since 2015. Despite these recurring outbreaks, genomic data on the H5 lineages circulating within Laos after 2018 remained limited.
To investigate the genetic characteristics of these circulating pathogens, researchers sequenced 37 isolates collected from 2019 to 2024 and evaluated them using phylogenetic analyses alongside publicly available Lao avian influenza sequences gathered between 2015 and 2024.
Based on gene constellations, the investigators identified 12 distinct genotypes spanning three hemagglutinin clades. These comprised seven genotypes within clade 2.3.2.1e designated E1 through E7, three genotypes within clade 2.3.4.4b designated B1 through B3, and two genotypes within clade 2.3.4.4h designated H1 and H2.
Clade 2.3.2.1e H5N1 viruses predominated overall during the study window, generating novel genotypes through reassortment events involving clade 2.3.4.4b H5N1 and Eurasian low-pathogenicity avian influenza viruses. In contrast to this dominant lineage, clade 2.3.4.4b H5Nx and clade 2.3.4.4h H5N6 viruses were identified only sporadically.
Phylogenetic comparisons demonstrated that genetically related clade 2.3.2.1e H5N1 genotypes co-circulated across Laos, Cambodia, and Vietnam, while clade 2.3.4.4b H5N1 strains identified in Laos in 2023 clustered with viruses documented in East Asia and North America since 2021.
The analysis also highlighted zoonotic and cross-species concerns among specific lineages. Genotype H2, representing a clade 2.3.4.4h H5N6 virus, was genetically similar to H5N6 strains epidemiologically linked to a human infection in Laos and detected in both poultry and human patients in China.
Additionally, genotype E7 was detected continuously from 2022 to 2024, exhibiting the identical gene constellation found in viruses associated with human and mammalian infections in Cambodia and Vietnam. The researchers noted that these findings underscore the persistent circulation and reassortment of H5 viruses in Laos, demonstrating the need for sustained genomic surveillance to track transboundary transmission and zoonotic risks across Southeast Asia.
Subject of Research: Genomic diversity and reassortment of H5 avian influenza viruses in Laos
Article Title: Genetic diversity of H5 high pathogenicity avian influenza viruses detected in Laos, 2019–2024: multiple clades, subtypes, and genotypes
Article References: Kim, J.-M., Jang, Y., Cha, R. M., Theppangna, W., Phommachanh, P., Park, M.-J., Lim, E. H., Lee, Y.-N., Lee, Y.-J., & Lee, E.-K. (2026). Genetic diversity of H5 high pathogenicity avian influenza viruses detected in Laos, 2019–2024: multiple clades, subtypes, and genotypes. Frontiers in Veterinary Science, 13, Article 2002252. https://doi.org/10.3389/fvets.2026.2002252
Image Credits: AI Generated
DOI: 10.3389/fvets.2026.2002252
Keywords: Avian Influenza, H5N1, Laos, Genomics, Phylogenetic Analysis, Viral Reassortment, Zoonotic Risk, Infectious Diseases, Genetic, diversity, high, pathogenicity
News Source: Kristina Jarvis. (November 12, 2026). Study Identifies Twelve Avian Influenza Genotypes Circulating Across Laos. Scienmag.
