Abstract

Background Influenza A Viruses (IAV) are emerging pathogens of public health concern. Wild birds and mammals are important reservoirs that contribute to the evolving genetic diversity of influenza viruses and represent an important transmission interface that may facilitate mammalian adaptation of IAV. Detection of IAV within wild mammalian species provides important insights to potential mechanisms of interspecies transmission and adaptation. Methods A novel H3N6 IAV was recovered from a stranded harbor seal (Phoca vitulina) in Alaska. The virus was sequenced, isolated, and tested for replication in mouse and ferret models. Results Analysis of the full genome sequence suggested the novel seal derived H3N6 IAV was derived from a reassortment of H3N8 and H4N6 circulating in dabbling ducks in the Pacific flyway. Assessment of replication and virulence phenotypes in mouse and ferret models of influenza provided evidence of replication in mammals despite minimal disease. Conclusions. We report the first identification of H3N6 within marine mammals with capacity for replication within mammalian hosts despite the absence of previously described adaptations. Field surveillance studies combined with risk assessment pipelines that incorporate phylogenetic analysis and in vitro and in vivo characterization are essential for understanding mammalian adaptation.