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Spread among captive mink could give the H5N1 strain opportunities to evolve and adapt to mammals. When mink at a big farm in Galicia, a region in northwestern Spain, started to die in October 2022, veterinarians initially thought the culprit might be SARS-CoV-2, which has struck mink farms in several other countries. But lab tests soon revealed something scarier: a deadly avian influenza virus named H5N1. Authorities immediately placed workers on the farm under quarantine restrictions. The more than 50,000 mink at the facility were killed and their carcasses destroyed. None of the farm workers became infected. But the episode, described in a paper in Eurosurveillance last week, has reignited long-smoldering fears that H5N1 could trigger a human pandemic. The virus is not known to spread well between mammals; people almost always catch it from infected birds, not one another. But now, H5N1 appears to have spread through a densely packed mammalian population and gained at least one mutation that favors mammal-to-mammal spread. Virologists warn that H5N1, now rampaging through birds around the world, could invade other mink farms and become still more transmissible. “This is incredibly concerning,” says Tom Peacock, a virologist at Imperial College London. “This is a clear mechanism for an H5 pandemic to start.” Isabella Monne, a veterinary researcher at the European Union’s Reference Laboratory for Avian Influenza in Italy, where the samples from Spain were sequenced, calls the finding “a warning bell....
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The cluster is the first known instance of likely animal-to-human transmission in the United States. In the first year of the pandemic, at least four people in Michigan were infected with a version of the coronavirus observed mostly in mink, the Centers for Disease Control and Prevention confirmed on Monday. The cluster, which previously included just three cases, represents the first known instance of possible animal-to-human transmission of the virus in the United States. Two of the infected were employees of a Michigan mink farm that experienced a coronavirus outbreak in October 2020. The other two had no known links to the farm, suggesting that the mink variant may have been circulating more widely among area residents at the time. Samples of the virus collected from all four people contained two mutations that scientists have hypothesized may be signs of adaptation to mink, Dr. Casey Barton Behravesh, who directs the C.D.C.’s One Health Office, said in an email on Monday. The mutations have previously been documented in farmed mink in Europe, as well as in people with connections to those farms. “This, in addition to the mink farm workers testing positive for Covid-19 after the mink herd had begun experiencing illness and increased mortality, suggests that the most likely hypothesis is that the workers were infected after contact with mink on the farm,” Dr. Barton Behravesh said. But that cannot be conclusively proved, she noted. “Because there are few genetic sequences available from the communities around the farm, it is impossible to know for sure whether the mutations came from mink on the farm or were already circulating in the community,” she said. National Geographic first reported the fourth human case, after obtaining government documents about the mink farm outbreak under the Freedom of Information Act. Last year, The Detroit Free Press and the Documenting Covid-19 project reported on the first three cases, which included the two farm workers and a taxidermist who had no known connection to the mink farm, according to emails obtained by the two organizations. On Monday, they reported that the fourth case had been the taxidermist’s wife. In early October 2020, Michigan officials announced that the virus had been detected in mink on a local farm and that several of the animals had died. Upon the state’s request, the C.D.C. deployed a team to help investigate the outbreak. The investigators collected samples from animals and human workers on the farm, as well as people in the surrounding community, Dr. Barton Behravesh said. In March 2021, the C.D.C. updated its website to note that a “small number of people” had contracted a version of the virus that “contained unique mink-related mutations.” “This suggests mink-to-human spread might have occurred,” the agency said, noting that all of the human patients had recovered. But the first human cases, in two workers on the affected mink farm, were identified as early as Nov. 4, months before the agency updated its website, National Geographic reported. “C.D.C. became aware of genetic sequencing data indicating possible mink-to-human transmission in late 2020,” Dr. Barton Behravesh said. The agency then worked with other federal and state officials to analyze that data, she added: “Information was published on the C.D.C. website as soon as it became clear there was possible mink to human spread.” Mink-to-human transmission has also been reported in Denmark, the Netherlands and elsewhere. Overall, transmission of the virus from animals to humans is believed to be rare. Humans are far more likely to spread the virus to one another, or to other species, than they are to catch it from animals, experts say.
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Agriculture minister says origins of outbreak unclear after seven farm workers – and 87% of the mink – test positive. Spain has ordered the culling of nearly 100,000 mink on a farm after confirming many were carrying coronavirus, a regional minister said on Thursday. Joaquin Olona, agriculture minister for the north-eastern Aragon region, said the cull would involve the slaughter of 92,700 mink which are prized for their pelt. Officials suspect the virus first reached the farm through a worker who passed it on to the animals. But Olona said it was not completely clear if “transmission was possible from animals to humans and vice versa”. In the Netherlands tens of thousands of mink have been slaughtered since the start of the pandemic after 20 farms were found to be infected, the Dutch authorities said earlier this month. The move came after at least two farm workers were found to be infected in May, most likely by the mink, with the World Health Organization saying it could be the first known cases of animal-to-human transmission. In Spain the mink farm – in Puebla de Valverde, about 100km (60 miles) north-west of the coastal resort of Valencia – has been carefully monitored since 22 May after seven workers tested positive for Covid-19, Olona said. Since then no animals have left the property, which is the only mink farm in Aragon. Officials have since carried out a string of PCR tests which on 13 July showed that 87% of the mink were infected, prompting the decision to carry out a cull “to avoid the risk of human transmission”, Olona said....
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In October 2022, an outbreak in Europe of highly pathogenic avian influenza (HPAI) A(H5N1) in intensively farmed minks occurred in northwest Spain. A single mink farm hosting more than 50,000 minks was involved. The identified viruses belong to clade 2.3.4.4b, which is responsible of the ongoing epizootic in Europe. An uncommon mutation (T271A) in the PB2 gene with potential public health implications was found. Our investigations indicate onward mink transmission of the virus may have occurred in the affected farm. Published in Eurosurveillance (Jan. 18, 2023): https://doi.org/10.2807/1560-7917.ES.2023.28.3.2300001
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Denmark, the world's largest producer of mink furs, plans to cull all mink in the country to contain a mutated form of novel coronavirus. Prime Minister Mette Frederiksen said Wednesday the decision had been made with a "heavy heart," but it was necessary based on the recommendation of health authorities. "The virus has mutated in mink. The mutated virus has spread to humans," Frederiksen said. Statens Serum Institut, the Danish authority based in Copenhagen which deals with infectious diseases, had found five cases of the virus in mink farms and 12 examples in humans that showed reduced sensitivity to antibodies, she said. Allowing the virus to spread could potentially limit the effectiveness of future vaccines. "We have a great responsibility towards our own population, but with the mutation that has now been found, we have an even greater responsibility for the rest of the world as well," Frederiksen said. There are between 15 million and 17 million mink in Denmark, according to authorities. Outbreaks of coronavirus at the country's mink farms have persisted despite repeated efforts to cull infected animals since June. One million mink within a five mile (8.4 kilometers) radius of suspected or confirmed farm infection were destroyed in October. Denmark's police, army and home guard will be deployed to speed up the culling process, Frederiksen said. Mink have also been culled in the Netherlands and Spain after infections were discovered there. The Prime Minister said new restrictions will be introduced in certain areas of Denmark to contain the spread of the mutated virus, including Hjorring, Frederikshavn, Bronderslev, Jammerbugt, Vesthimmerland, Thisted and Laeso municipalities. "Unfortunately, the residents of those municipalities have to prepare for further restrictions in the near future," she said.
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