Molecular characterization and genetic analysis of highly pathogenic H5N1 clade 2.3.4.4b in seagulls from Dukan Lake, Iraq.

Avian influenza virus (AIV) remains a significant global threat, with periodic reemergence in Iraq. This study marks the first molecular characterization of the highly pathogenic avian influenza (HPAI) H5N1 clade 2.3.4.4b in seagulls. The H5N1 AIV was identified during outbreaks in 2024 at Dukan Lake in Sulaimani province. Phylogenetic analysis of the HA gene revealed that the Dukan Lake strain belongs to subclade 2.3.4.4b, clustering closely with Kazakhstan HPAI strains (A/mute swan/Mangystau/1-S24R-2/2024(H5N1) and (A/Cygnus cygnus/Karakol lake/01/2024(H5N1)), with DNA identities of 99.38% and 98.82%, respectively. Genetic analysis showed a polybasic amino acid cleavage site motif (PLREKRRKRGLF) in the HA gene. Additionally, receptor-binding domain (RBD) analysis indicated a preference for the avian α-2, 3 Sialic acid (SA) receptor over the mammalian α-2, 6 SA receptor. The NA gene analysis revealed amino acid residues D199, I223, S247, and H275, which are susceptible to antiviral drugs. The molecular analysis of the H5N1 Dukan Lake seagull strain provides insights into how the virus spreads among different species and countries, which is crucial for global health security and the development of effective control measures.