Divergent Reassortment and Transmission Dynamics of Highly Pathogenic Avian Influenza A(H5N8) Virus in Birds of China During 2021

Abstract

Highly pathogenic influenza A(H5N8) viruses had caused several outbreaks among wild bird and poultry populations across the globe, and strikingly, caused human infection, posing serious public health concerns. In this study, we conducted influenza surveillance in China during 2021 to monitor the evolution of influenza viruses in poultry. A total of 35 influenza viruses were obtained in chickens, ducks, and geese, of which 30 H5N8 viruses, 3 H5N1 viruses, and 2 H5N6 viruses. Phylogenetic analysis suggested all of H5N1, H5N6, and H5N8 isolates were derived from clade 2.3.4.4b H5N8 viruses during 2020/21 season, and notably, the internal genes of H5N1 and H5N6 viruses shared different genetic heterogeneity with H5N8 viruses and had been reassorted with wild bird-origin H5N1 viruses from Europe. By contrast, almost all H5N8 viruses exhibited only one phylogenic cluster with wild bird-origin H5N8 viruses in China and Korea, indicating that H5N8 viruses in China were more stable. Besides, we found that Korea is the main output geographic location in the spread of these H5N8 viruses to northern and eastern China, and especially, the co-circulation of H5N8 viruses occurred within China, with central China acted as a seeding population during the H5N8 epidemic. The statistical support was strong for viral migration from wild birds to chickens and ducks, indicating that 2.3.4.4b poultry-origin H5N8 viruses during 2020–2021 were originated from wild birds. Our findings provide novel insights into evolution and transmission dynamics of H5 subtype influenza viruses among poultry after novel H5N8 viruses invaded China for nearly one year.

Genetic and antigenic analyses of H5N8 and H5N1 subtypes high pathogenicity avian influenza viruses isolated from wild birds and poultry farms in Japan in the winter of 2021–2022

“…This hypothesis was supported by the results of the cross-neutralization test: G2b group Miya32 was antigenically distinct from the G2a group H5N8 HPAIV strains. In the winter of 2020–2021, H5N8 HPAIVs caused outbreaks in East Asian countries [ 3 , 21 , 38 ], suggesting that a considerable number of migratory bird populations contracted to HPAIVs and contributed to the selection of the most recent H5N1 HPAIVs as circulating strains. The history of previous H5N8 HPAIV infections might reflect the overall HPAI circumstances in Japan in the winter of 2021–2022; HPAIV infection cases were predominantly observed in sedentary raptors and crows compared with migratory waterbirds (see Supplementary Table 1 ).…”

“…Similarly, a shift in circulating HPAIVs subtypes has been observed in East Asian countries. In the winter of 2020–2021, H5N8 HPAIVs caused outbreaks in China, South Korea, and Japan [ 3 , 21 , 38 ]. At least seven gene constellations, genotypes E1–E7, have been found in causal H5N8 HPAIVs [ 3 ].…”

A single immunization with H5N1 virus-like particle vaccine protects chickens against divergent H5N1 influenza viruses and vaccine efficacy is determined by adjuvant and dosage

“…H5N1 AIV has continued to infect people worldwide since 2003, as of 14 July 2023, a total of 878 laboratory-confirmed cases of H5N1 AIV infection were reported to WHO, including 458 deaths [ 4 ]. Currently, H5N1 subtype HPAIV revealed a novel propensity after continuous evolution in nature, such as reassort with other influenza virus neuraminidase (NA) subtypes, including H5N6 and H5N8 [ 5 , 6 ]. This undoubtedly increases the risk of the H5 subtype HPAIV outbreak; thus preventing the H5N1 subtype HPAIV pandemic is imperative.…”