Highly Pathogenic Avian Influenza A(H5N1) Virus Outbreak in New England Seals, United States

We report the spillover of highly pathogenic avian influ-enza A(H5N1) into marine mammals in the northeastern United States, coincident with H5N1 in sympatric wild birds. Our data indicate monitoring both wild coastal birds and marine mammals will be critical to determine pandemic potential of influenza A viruses.