Mink-farm outbreak reveals chicken flu can unfold between mammals


Minks at a farmer's estate where all minks must be culled due to a government order on November 7, 2020 in Bording, Denmark.

The brand new variant of H5N1 flu had been spreading amongst mink.Credit score: Ole Jensen/Getty

An outbreak of avian influenza on a mink farm in Spain supplies the strongest proof to this point that the H5N1 pressure of flu can unfold from one contaminated mammal to a different.

The outbreak of H5N1 flu, described in a report in Eurosurveillance on 19 January1, occurred on an American mink (Neovison vison) farm in Carral in October 2022. Genetic sequencing confirmed that the animals have been contaminated with a brand new variant of H5N1, which incorporates genetic materials from a pressure present in gulls, in addition to a genetic change identified to extend the flexibility of some animal-flu viruses to breed in mammals.

The brand new variant places chicken flu in “uncharted territory”, says Wendy Puryear, a virologist at Tufts College in Medford, Massachusetts. Researchers have warned that, with out cautious precautions, the illness may ultimately unfold amongst folks.

Leaping species

Over the previous yr, H5N1 has proven an growing potential to leap from birds to mammals. In the US, infections have been present in a couple of dozen species, together with raccoons, foxes, seals and grizzly bears.

Till this specific outbreak, all mammalian infections may very well be attributed to direct contact with virus-contaminated materials, says Hualan Chen, a virologist on the Harbin Veterinary Analysis Institute in China. For instance, animals that ingest wild-bird droppings, or that prey on contaminated animals, can develop the illness. However its unfold between mammals “implies that this H5N1 virus might pose the next danger to public well being”, Chen says.

In the course of the first week of October 2022, staff on the affected mink farm observed that the minks’ mortality charge had elevated from a baseline of 0.25% per week to 0.77%, prompting checks on the affected animals for the H5N1 and SARS-CoV-2 viruses. The animals examined optimistic for H5N1. Within the following weeks, extra animals fell sick, and the illness appeared to unfold from ‘sizzling spots’ of between two and 4 pens, by which all animals turned contaminated and died. Staff have been compelled to cull all 51,986 mink on the farm. Eleven farm staff have been in touch with the contaminated mink, however all examined detrimental for H5N1.

“This species may function a possible mixing vessel for the interspecies transmission amongst birds, mammals and human,” the report’s authors write. “It’s essential to strengthen the tradition of biosafety and biosecurity on this farming system and promote the implementation of advert hoc surveillance packages for influenza A viruses and different zoonotic pathogens.”

Stopping unfold

Measures taken to forestall the brand new pressure from spreading past the farm appear to have been “vigorous, complete and profitable”, says infectious-disease specialist William Schaffner at Vanderbilt College Medical Middle in Nashville, Tennessee.

However Puryear thinks that as a result of the brand new variant incorporates genetic materials from gull flu, it’s seemingly that at the least a few of its genetic adjustments arose in gulls earlier than coming into the mink farm. Because of this a pressure containing these mutations might be nonetheless circulating within the chicken inhabitants. However for human populations, the outlook continues to be good: if the brand new pressure did begin to infect folks, well being authorities may in all probability produce a vaccine rapidly, and the antiviral drug Tamiflu can scale back the severity of the illness.

The potential danger to wild animals is bigger. Chicken flu has persistently brought about excessive ranges of illness and demise amongst wild birds and mammals over the previous yr, and the way the brand new variant will have an effect on that development stays to be seen. “We simply merely don’t know,” says Puryear.

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