Two dolphins and a harbour porpoise have died from bird flu in British waters, the UK government said.
The dolphins were found in different areas, on beaches in Devon and Pembrokeshire, while the harbour porpoise was found in East Yorkshire.
The deaths are the first recorded in the UK of dolphins related to the virus, which is known as H5N1.
They come amid the largest ever H5N1 pandemic in birds, which has killed millions worldwide over the past 18 months.
Many were slaughtered to stop the disease from spreading, but there have been tens of millions of bird deaths in the wild.
The disease has also been discovered in other animals, including badgers, black bears, bobcats, coyotes, ferrets, fisher cats, foxes, leopards, opossums, pigs, skunks and sea lions.
It is believed other species become infected after scavenging on infected wild birds.
H5N1 is a type of influenza virus, predominantly harboured by birds, that was first detected on a goose farm in China in 1996.
The virus is highly pathogenic to birds, meaning infections often cause extreme symptoms, including death.
There have been relatively few human infections detected — fewer than 900 documented globally over several decades — but about half of those infected individuals have died.
The UK government recently stepped up monitoring for the virus after it was discovered in otters and foxes.
The discovery was made after employees at the UK's Animal and Plant Health Agency tested 66 mammals for avian flu. Nine otters and foxes were found to be infected.
Since then officials have been carrying out targeted testing and surveillance in animals and humans exposed to the virus.
In November, officials in the UK instructed all poultry and captive birds in England to be kept indoors in an effort to prevent the spread of the virus.
Hundreds of cases have been confirmed at commercial premises, smallholdings and in pet birds since October last year.
And earlier this year a pet cat was euthanised after suffering from severe neurological symptoms due to a case of bird flu it picked up from a nearby poultry farm that raised ducks.
Experts have stressed the risk to humans is low, but acknowledge there is a possibility it could one day jump to humans.
It currently does not spread well between people and most of those who have contracted H5N1 have got it directly from interacting with infected poultry — specifically chickens, turkeys, ducks and geese, which often are raised in close quarters on large commercial farms.
Since the outbreak began a year ago, a small number of cases have been detected in people.
An 11-year-old Cambodian girl died on February 22 at a hospital in the capital, Phnom Penh, shortly after tests confirmed she had Type A H5N1 bird flu.
Her father tested positive for the virus the day after her death, but did not develop serious symptoms and was eventually released from hospital.
However, scientists have warned they have seen changes in the virus from samples from a mink farm in Spain which could more easily replicate in mammalian tissue.
Why don’t we make a vaccine just in case?
With avian influenza viruses, it is not possible to make effective human vaccines in advance, because it is not known exactly what the genetics of the virus will be if it starts to spread in humans.
The seasonal flu vaccine must be remade every year, even though the general types of flu viruses that it protects against are the same, because the specific genetic variants that affect humans change from year to year.
Right now, experts say the best way people can protect themselves from H5N1 is to avoid contact with infected birds.
