Four dead seals have tested positive for bird flu in Scotland, as the number of cases of highly pathogenic avian flu in mammals continues to grow globally with experts warning of “a step-change” in its spread.

The largest ever bird flu outbreak had already spilled over into otters and foxes in the UK, with about 70 mammals having tested positive for the (HPAI) H5N1 virus. The seal carcasses were sent for screening last year and the results have come back positive, the Guardian reported.

“Three out of the four harbour seals and one of the two grey seals from 2021 and early 2022 tested positive for HPAIV H5N1,” said Scottish Marine Animal Strandings Scheme in a statement. The animals were found in Aberdeenshire, Highlands, Fife and Orkney. “We also want to check our more recent cetacean cases for evidence of spillover,” it said.

As well as ripping through wild bird populations around the world, H5N1 has been found in dolphins, domestic cats, leopards and grizzly bears. Recently, the Peruvian government said nearly 580 sea lions had died from it in seven protected marine areas.

Generally it is believed mammals are getting infected by scavenging on dead or sick wild birds, but sea lions live in colonies. This has raised concerns it could now be spreading within mammal populations in the wild. (Photo by Kevin Mueller on Unsplash)

The virus is also devastating wild bird populations across the globe, meaning it is reaching places previously never exposed to such diseases. This means they can carry it to the most pristine parts of the planet, possibly spreading it into other endangered species.