“As far as we know this is the first confirmed case in the world of bird flu in a porpoise,” veterinarian Elina Thorsson said in a statement. “It is likely that the porpoise somehow came into contact with infected birds,” she said.

The young male was found stranded, alive, on a beach in western Sweden in late June. Despite efforts from the public to get it to swim out to deeper
waters, it was suffering from exhaustion and died the same evening.

The bird flu virus, H5N1, was found in several of its organs. “Contrary to seals, where illnesses caused by a flu virus have been detected multiple times, there have been only a handful of reports of flu virus in cetaceans”, Thorsson said.

The virus has also previously been detected in other mammals, including red foxes, otters, lynx and skunks, the institute said.

Europe and North America are currently seeing a vast outbreak of bird flu among wild birds.