Influenza A(H1N9) virus in red knots

Highly pathogenic avian influenza (HPAI) strains are deadly to domestic poultry and can wipe out entire flocks within days. Low-pathogenicity avian influenza (LPAI) strains typically cause few or no signs of illness in birds.

Wild birds carry a wide range of influenza viruses, and migrating species can introduce pathogens into new regions, as seen with HPAI A(H5N1).

Birds also provide a useful system for studying how ecology and evolution shape viral communities, although the drivers of viral diversity remain incompletely understood, particularly in isolated regions. Host phylogeny, life history, and environment all influence virome composition, and scavenging behaviour may further increase viral exposure.

Scientists considered Aotearoa/New Zealand, which is connected by major flyways yet geographically isolated, an ideal setting to examine how behaviour and ecology structure viral communities[1].

Although no HPAI viruses were detected, researchers identified the complete genome of a low-pathogenic A(H1N9) avian influenza virus, designated A/Red knot/Firth of Thames/1/2024 (H1N9), in red knots (Calidris canutus) sampled from the Firth of Thames on mainland New Zealand. Phylogenetic analysis of the hemagglutinin (HA) segment showed close clustering (more than 90% nucleotide similarity) with H1 viruses previously sampled in Oceania and Asia. Available evidence indicates this LPAI lineage was not a recent introduction to New Zealand.

Detection of this Low-pathogenicity avian influenza A(H1N9) virus highlights the value of continued surveillance of migratory shorebirds. While influenza A viruses can evolve and occasionally spill over to other hosts, H1 subtypes do not typically convert to highly pathogenic forms through simple mutations in the same way that H5 or H7 viruses can.

At present, this particular virus is considered low-risk for both poultry and humans, but ongoing monitoring remains important for early detection of any changes.

[1] Waller et al: Viral community structure in New Zealand’s aquatic birds is associated with scavenging behavior in Current Biology – 2026. See here.