We report the spillover of highly pathogenic avian influenza 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.
Keywords: Caniformia; H5N1; New England; United States; avian influenza; ecology; gray seals; harbor seals; influenza; virology; viruses; zoonoses.