Since their introduction into North America in late 2021, clade 2.3.4.4b high pathogenicity avian influenza (HPAI) H5Nx viruses have become endemic and reassorted extensively with co-circulating low pathogenicity avian influenza (LPAI) viruses, generating diverse genotypes and phenotypes. In early 2024, the novel D1.1 reassortant emerged in the North Pacific flyway and was associated with multiple human H5N1 infections and by December was the dominant North American HPAI genotype. Although waterfowl are the natural reservoir of avian influenza viruses, research has focused largely on ducks. Geese remain comparatively understudied, partly because of historically lower LPAI prevalence, despite accounting for 40.3% of HPAI-positive samples during the 2024 D1.1 wave. HPAI dynamics in non-migratory geese living year-round near humans remain particularly poorly characterized.
On 1 November 2025, a citizen observer reported a lethargic Canada goose (Branta canadensis) exhibiting head tilt in an urban park lake in Memphis, Tennessee, USA. The bird was found dead the following day. Leg band 1298-09581 identified it as an adult female banded four years earlier, on 2 July 2021, approximately two miles from the recovery site, supporting membership in the local resident population. No other ducks or geese were known to be concurrently affected in the park.