The case adds another worrying wrinkle to a global outbreak that has devastated bird and marine mammal populations, and recently appeared in cattle herds.
The F.D.A. is expected to approve a new round of shots by Pfizer and Moderna as early as Monday to prepare Americans for the fall and winter season when infections usually tick upward.
The F.D.A. is expected to approve a new round of shots by Pfizer and Moderna as early as Monday to prepare Americans for the fall and winter season when infections usually tick upward.