Influenza Virus Dynamics in Avian Reservoirs

Influenza A viruses circulate in a wide range of wild and domestic bird species, forming a complex ecological network that underpins viral maintenance, evolution and occasional spill-over into mammalian hosts. Aquatic birds, in particular waterfowl and shorebirds, act as long-term reservoirs in which low-pathogenic avian influenza (LPAI) viruses replicate in the gastrointestinal tract without causing overt disease. Seasonal migration and congregation at shared breeding or staging sites facilitate virus exchange among geographically disparate populations, driving genetic reassortment and the emergence of novel subtypes. From this gene pool, highly pathogenic avian influenza (HPAI) strains may occasionally arise following insertional mutations at the haemagglutinin cleavage site, leading to systemic infection in poultry and increased zoonotic potential. Surveillance of viral diversity in wild birds is thus critical to detect shifts in clade distribution, to track the global spread of virulent lineages and to foresee threats to animal and human health. Recent advances in high-throughput sequencing, phylogeographic modelling and experimental characterisation of receptor specificity have illuminated the mechanisms by which avian influenza viruses persist, diversify and adapt to new hosts, informing both vaccination strategies in poultry and risk assessments for pandemic preparedness.

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Influenza Virus Dynamics in Avian Reservoirs publication trend

The graph below shows the total number of articles in influenza virus dynamics in avian reservoirs across all publications each year (not limited to Nature Index journals).

Technical terms

Avian reservoir: Wild or domestic bird populations that maintain and shed influenza A viruses without severe disease, enabling long-term viral persistence.

Clade: A phylogenetic grouping of influenza virus strains sharing a common ancestor, often defined by percentage sequence divergence in the haemagglutinin gene.

Haemagglutinin cleavage site: A specific region in the viral HA protein where host proteases cleave to activate membrane fusion and entry into host cells; insertion of basic residues here increases pathogenicity in poultry.

PB2: Polymerase basic protein 2, a subunit of the viral RNA polymerase complex; mutations at residue 627 or 701 facilitate replication efficiency and transmission in mammalian hosts.

Receptor-binding specificity: The preference of viral haemagglutinin for sialic acid linkages—α2,3 in avian cells versus α2,6 in human respiratory epithelium—determining host range and zoonotic potential.

References

1. Nomenclature updates resulting from the evolution of avian influenza A(H5) virus clades 2.1.3.2a, 2.2.1, and 2.3.4 during 2013–2014. Influenza and Other Respiratory Viruses (2015).
2. Genetics, Receptor Binding Property, and Transmissibility in Mammals of Naturally Isolated H9N2 Avian Influenza Viruses. PLOS Pathogens (2014).
3. H7N9 virulent mutants detected in chickens in China pose an increased threat to humans. Cell Research (2017).
4. Transmission of Influenza Virus in a Mammalian Host Is Increased by PB2 Amino Acids 627K or 627E/701N. PLOS Pathogens (2009).