A Washington state resident has tested positive for bird flu, marking the first human case in the U.S. in nine months, and with a strain only seen in animals before.

Since late 2021, a panzootic, or "a pandemic in animals," of highly pathogenic bird flu variant H5N1 has devastated wild birds, agriculture, and mammals. Unlike previous outbreaks, aggressive culling of domestic birds has not contained it,

It was a quiet summer for bird flu: Egg prices fell a bit, fewer sick poultry flocks were culled on farms, and officials took a breath. “It was lovely,” said Shauna Voss, the assistant director of the Minnesota Board of Animal Health. But it didn’t last.

After a summer lull in U.S. cases of avian influenza in both poultry and dairy cattle—and no human infections reported in the country since February—the virus is back. The currently circulating bird flu subtype H5N1 is here to stay. “We’ve resigned ...