Scientists are on high alert for a new influx of bird flu as seabirds return to UK shores in large numbers for the nesting season.
A second summer mass die-off will have devastating effects on populations of gannets and some other species.
It also increases the risk of virus transmission to mammals.
In an exclusive interview, the government’s Animal and Plant Health Agency (APHA) director of scientific services, Professor Ian Brown, told Sky News the source of the virus that killed the animals last year remains unclear.
“It appears that this virus was introduced into seabird populations by another population,” he said.
“So instead of those gannets going out to sea and being exposed to the virus, it’s more likely that they were exposed to other birds that were mixed in with their flock.
“We know seagulls are susceptible to this virus, they can carry it and shed it. So in theory they could introduce this virus into the flock.
“Once it gets into the colony, the birds are packed so densely that the virus spreads very quickly.”
this H5N1 virus Thousands of seabirds died last year.
After wintering at sea, gannets, guillemots, puffins and kittiwakes begin congregating in large numbers on the steep cliffs to raise their young.
“Hopefully the birds will come back and have a healthy breeding season and they won’t be exposed to the virus,” Professor Brown said.
“But knowing what happened last summer, we have to be more vigilant and look for early events that might indicate a resurgence of the virus.”
Volunteers and rangers from the Royal Society for the Protection of Birds (RSPB) are checking the habitat of sick birds and scanning the sea for dead birds.
Half a million seabirds nest at Bempton Cliffs Nature Reserve yorkshire coastal. So many gannets congregate here that it is of international importance for the species.
But in the most crowded areas of the habitat, 80 percent of gannet chicks died last year.
They almost certainly starved to death, said Dave O’Hara, the RSPB’s senior site manager.
“We speculate this is because one or two of the adults had died,” he said.
“The killing of adult birds is particularly concerning because they only have one chick per year. So it could take a long time [for the population] recover.
“This year, there’s been a lot of concern about what’s to come.”
First identified in 1996, the H5N1 virus was common until two years ago, causing small outbreaks in poultry and migrating ducks and geese at certain times of the year.
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But a new variant called 126.96.36.199b has taken the world by storm. It is now widespread in wild birds and is no longer just a seasonal disease.
It has also begun infecting mammals across species, including foxes, seals and dolphins in the UK. It is likely that all died from eating infected birds.
There is no evidence of mammal-to-mammal transmission in the UK, although this has occurred in a mink farm in Spain and possibly in sea lions in South America.
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But APHA is keeping a close eye on a mutation called E627K, which has been found in eight out of 10 samples taken from UK mammals and appears to increase airborne virulence and capacity.
“What we’re tracking are changes in viruses that are rarely observed in bird populations,” Professor Brown said.
“They likely indicate that the virus is making some adjustments. But an adjustment alone is not enough for a virus to spread successfully from one mammal to another.
“The numbers game is a factor. The more exposed you are, the greater the risk that these events may trigger and trigger something that can spread, and that’s why we monitor.”
There have been seven cases of the new strain among people in close contact with birds, including one in the UK. All people in the US or Europe had mild or no symptoms.
The HPA said the risk to the public was low and there had been no cases of human-to-human transmission.
But it warned people not to touch dead or sick birds and to wash their hands after feeding the birds.