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Massive seal death raises fears bird flu could spread between mammals, threatening another pandemic

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Scientists are investigating the possibility that bird flu was transmitted between mammals in the wild for the first time – fueling fears it could lead to the next pandemic in humans.

In what is being described as a ‘mass kill event’, more than 700 seals were found dead in December in the Caspian Sea, near where the highly contagious H5N1 variant of bird flu was discovered in birds wild months earlier.

Scientists at Dagestan State University have identified bird flu in the tissues of dead seals, although it’s too early to say whether that was the cause of death or whether the animals passed it on to each other.

The situation is being monitored by the British government, I learned, with Defra and the UK Health Security Agency receiving regular updates.

Seals and other mammals have been infected with bird flu directly from birds before, but so far the only recorded incidents of mammalian-to-mammal transmission involve mink kept in close captivity on a farm in Spain.

If the H5N1 variant has adapted to jump from one mammal to another, virologists fear that it could take another evolutionary leap to become transmissible between humans and trigger a pandemic.

There is currently no evidence that the virus can be transmitted between humans. Since the start of the last global H5N1 outbreak a year ago, fewer than 10 people have caught the virus, directly through close contact with poultry or other birds, and only one human death has been reported.

But samples from four mink who caught H5N1 during an outbreak at a mink farm in Galicia, northwestern Spain, in October revealed changes to the virus, including a mutation called T271A which can more easily replicate in mammalian tissues.

If bird flu is confirmed to have been transmitted between seals in the cSea, it would be the first known transmission between mammals in the wild.

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Dr Tom Peacock, a virologist at Imperial College London, said I“If this is found to be sustained transmission in a wild mammalian species, this is yet another worrying ‘first’ with these H5N1s that should not be ignored. This would be further proof that these H5N1s could be about to cause the next pandemic.

Defra is aware of the developments in the Caspian Sea and the Dagestan State University report that it has identified avian influenza in seal tissue, I understand.

The latest risk assessment from the UK Health Security Agency says the risk to the human population from bird flu is “very low”, but there is evidence that the H5N1 strain has evolved to replicate more easily in the mammals.

The current threat is Level 3, i.e. there is “evidence of viral genomic changes that provide an advantage for mammalian infection”, which is below Level 4 evidence. one sustained mammal-to-mammal transmission, and two below level 5, human-to-human transmission.

H5N1 has been responsible for the deaths, both from infection and culling, of millions of birds in the UK and around the world as farmers were ordered to bring indoors the turkey and other free-range poultry starting last fall.

In the waters around Britain, stranded seals are collected and any possible cause of death is investigated for disease, including bird flu.

No seals, dolphins or whales have yet tested positive for bird flu in Britain during the current outbreak, which began in December 2021, but there have been previous cases in these marine mammals.

The UKHSA has advised people not to handle sick or dead poultry or other birds.

Announcing that avian influenza had been identified in Caspian seals, Dagestan State University said: “Preliminary studies on the mass mortality of Caspian seals showed that the animals were infected with avian influenza .

At the same time, it is too early to conclude that it was the virus that caused the death, research is continuing.”

Alimurad Gadzhiev, director of the DSU’s Institute of Ecology and Sustainable Development, said: “Specialists from the Institute of Ecology and Sustainable Development, together with colleagues from the Institute for Research in Virology and experts from the Compass Foundation, took tissue samples from dead seals.

in December to determine the cause of death. Based on the first results, we can say that the samples tested positive for bird flu. ยป

The incident in Dagestan was first reported by the Avian Flu Diary blog, which said: “Although we have seen a number of different influenza A viruses infect seals in the past – including H3N8, H10N8, H7N7, etc. –

HPAI H5N1 is the most obvious suspect right now. I hope we will have confirmation in the coming days.

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