…But when she and her colleagues went to a farm housing foxes and mink last week, the shrieking of the birds that normally surround the barns was gone, so thinned out were their flocks. Dead gulls littered the ground. The usual barking from the foxes was also missing.

“They were in such a bad condition,” Sironen said about the foxes she saw. She said she walked through two shelters, with some 100 meters of cages on both sides. Only a few had a healthy animal left. “Everything else was either dead or dying.”

The research team, decked out in full PPE, was witnessing the toll of the spread of a highly pathogenic avian influenza, H5N1, which has reached nearly every corner of the globe in recent years and decimated untold millions of birds, domestic and wild. But the virus hasn’t been restricted to birds. It is now causing outbreaks among mammals at a scale previously unseen, including in the past month at a number of Finnish fur farms, home to mink, foxes, and raccoon dogs.