Nomenclature Updates to the Hemagglutinin Gene Clade Designations Resulting From the Continued Evolution of High Pathogenicity Avian Influenza A(H5) Virus Clades 2.3.2.1c and 2.3.4.4

Lam TT, Davis CT; World Health Organization/World. Nomenclature Updates to the Hemagglutinin Gene Clade Designations Resulting From the Continued Evolution of High Pathogenicity Avian Influenza A(H5) Virus Clades 2.3.2.1c and 2.3.4.4. Influenza Other Respir Viruses. 2026 Oct;20(10):e7
submited by kickingbird at Oct, 9, 2026 9:59 AM from Influenza Other Respir Viruses. 2026 Oct;20(10):e7

Background and methods: The evolutionary divergence of the A(H5) hemagglutinin (HA) gene of high pathogenicity avian influenza (HPAI) viruses (A/goose/Guangdong/96 lineage) was analyzed by phylogenetic and average pairwise distance methods to identify clades that merit nomenclature updates.

Results and conclusions: Based on this assessment, 12 new clade designations were recommended based on division of clade 2.3.2.1c and 2.3.4.4 viruses, which were reported in Africa, Antarctica, Asia, Europe, the Middle East, the Americas, and Oceania since the most recent WHO/WOAH/FAO H5 Evolution Working Group update.