A bottlenose dolphin found dead in a Florida canal in the spring tested positive for a highly virulent strain of bird flu, scientists said on Wednesday. The announcement came a week after Swedish officials reported that they had found the same type of avian influenza in a stranded porpoise.
This version of the virus, which has spread widely among North American and European birds, has affected an unusually broad array of species. But these findings represent the first two documented cases in cetaceans, a group of marine mammals that includes dolphins, porpoises and whales.
It is too soon to say how commonly the virus infects cetaceans, but its discovery in two different species on two different continents suggests that there have “almost certainly” been other cases, said Richard Webby, an influenza virologist at St. Jude Children’s Research Hospital in Memphis.
“Our surveillance activities on a global scale are never sensitive enough to pick up the only two events of this kind,” said Dr Webby, who was not involved in the initial detection of the virus but is now working with the Florida team on follow-up studies.
This strain of bird flu is known as Eurasian H5N1.
While experts emphasise that the risk to humans remains low, the spread of the virus to new species poses potential risks to wildlife and provides the virus with new chances to mutate and adapt to mammalian hosts. Besides birds, the virus has earlier turned up in foxes, bobcats, skunks, and seals.