‘Incredibly worried’: Bird flu outbreak in Spanish mink farms sparks pandemic fears | Chemistry

When minks began dying on a large farm in Galicia, northwestern Spain, in October 2022, veterinarians initially thought SARS-CoV-2 was the culprit. But lab tests soon revealed something more terrifying. It is a deadly bird flu virus named H5N1. Authorities immediately placed workers on the farm under quarantine restrictions. While at the facility he killed over 50,000 minks and destroyed their carcasses.

None of the farm workers became infected. But that episode euro monitoring last week, Long-simmering fears that H5N1 could cause a human pandemic rekindledThe virus is not known to spread successfully between mammals. People most often become infected from infected birds. However, H5N1 now appears to have spread through dense populations of mammals and acquired at least one mutation that facilitates its spread from mammal to mammal. Virologists warn that H5N1, which is now rampant among birds around the world, could invade other mink farms and become even more contagious.

Tom Peacock, a virologist at Imperial College London, said: “This is very alarming. ‘This is a clear mechanism for the H5 pandemic to start.’ Italy where samples from Spain were sequenced Isabella Monne, a veterinary researcher at the European Union’s Reference Institute for Avian Influenza, calls the finding “an alarm bell.”

H5N1 was first detected in Chinese goose farms in 1996. A massive poultry outbreak in Hong Kong in 1997 led to the first documented human death and sparked the first pandemic scare. Around 2005, the virus splashed in migratory birds and has since spread around the world in several big waves. It spreads quickly and widely, and used to wreak havoc on the poultry industry in Europe and North America. Arrival in Latin America in fall 2022“This virus seems to be more adapted to all birds than to any other,” says Richard Webby, an influenza researcher at St. Jude Children’s Research Hospital.

H5N1 rarely infects mammals because the receptors to which the virus binds in the upper respiratory tract of birds are less common in the upper respiratory tract of mammals. But this time, many mammalian species were infected, including foxes, cats, ferrets, seals and dolphins, possibly through contact with infected birds. On January 17, Montana officials announced that three of his grizzly bear cubs, which were critically ill and euthanized in the fall, were also infected with his H5N1. People caught it too. So far, the current global wave has confirmed six human infections, including one death.

According to Thomas Mettenreiter, director of the Friedrich Loeffler Institute, 2.3.4.4b was less pathogenic to humans than previous versions, with some indications that about half of those infected died. Of course, that’s also bad news, as it could make it easier for the virus to start spreading under the radar, giving it more opportunity to evolve,” he says. The more often the virus infects a mammal, the higher the risk, he says, Webby. “This is a numbers game.”

Although there have been some reports of bird flu outbreaks in Chinese mink farms in the past, there is no clear evidence that the virus spread among animals. In the outbreak in Spain, there seems to be little doubt that it was. Theoretically, all sick animals could have picked up the virus from feed containing poultry by-products, but in areas with poultry farms and slaughterhouses supplying the feed, he suspected H5N1 outbreaks. Not reported. And when infected among minks, the virus spread from pen to pen as expected. Thijs Kuiken, a veterinary pathologist at Erasmus University Medical Center, said the chain of infection could have started when one animal caught and caged a sick bird.

It is not known how easily the virus found in Spain infects humans or spreads between humans. Sequenced virus samples from four mink show several alterations compared to avian viruses, including mutations in T271A, enzyme and polymerase genes. This change was also seen in other infected mammalian virus samples and is known to help H5N1 replicate better in mammalian tissues. But another worrisome mutation in the polymerase gene, E627K, didn’t appear, says Peacock, and the gene for hemagglutinin, a protein on the surface of the virus that hooks to host receptors, remained unchanged. “I might have been lucky with this one.”

According to Monne, her team and others are now studying the properties of the mink virus and the effects of the mutations it has accumulated. Among other things, they want to study the extent to which the virus is transmitted through close contact between animals. “We also plan to study aerosol infections,” she says.

The current outbreak has once again highlighted the risks of mink farming. Introduced to farms by humans, SARS-CoV-2 has spread like wildfire among animals, but has also returned to keepers. Researchers fear that the mink industry will become a permanent source of infection and a breeding ground for genetic mutations. Having already decided to phase out mink farming by 2024 for ethical reasons, the Netherlands has closed all remaining farms in 2021.

As for H5N1, Kuiken says farms pose an equally big threat. Most of the mammalian species that have been infected with viruses so far have been wild predators, scavengers feeding on infected birds, and “solitary animals, or animals that live in small families”. The virus is unlikely to spread far or infect humans. On mink farms, thousands of such solitary carnivores are forced to live together, creating ideal conditions for bird viruses to adapt to mammals. ’ says Kuiken.

At the very least, biosafety measures on mink farms need to be strengthened, Monne says. We need to reduce the risk of introduction. “They should take great care to keep animals away from wild birds.” PeaKok says it’s probably time to stop mink farming. “It’s a bit of an existential threat.”