Data Accessibility
All data supporting the findings of this study are openly accessible. Genetic sequences from IAV surveillance in Iceland are deposited in GenBank (https://www.ncbi.nlm.nih.gov/genbank) under accession numbers listed in Supplementary table 1b. Raw data used for the analysis are deposited in the Dryad Digital Repository (https://doi.org/10.5061/dryad.m37pvmd2m).