Viruses: Replication and Transmission of Influenza A Virus in Farmed Mink - 2026 EA H5N1 Outbreak In Utah Mink - Sept 28th Update on Utah Mink

[Michael Coston]

Viruses: Replication and Transmission of Influenza A Virus in Farmed Mink

#18,996

Mink are highly susceptible to both influenza A and SARS-CoV-2 infection, and over the past 16 years we've looked a a number of concerning spillovers, including:

• In 2009's That Touch Of Mink Flu, where at least 11 mink farms in the Holstebro municipality of Denmark were reported to be infected with a variant of the human H3N2 virus.
• Also in 2007, an antigenically distinct H3N2 Swine Influenza was detected in Canadian Mink, reported in a 2009 Journal of Clinical Microbiology study called Characterization of a Canadian Mink H3N2 Influenza A Virus Isolate Genetically Related to Triple Reassortant Swine Influenza Virus.
• A year earlier CIDRAP reported on a European mink found infected with an aggressive form of the H5 flu virusin the Blekinge region of southern Sweden near where H5N1 had been detected in wild birds.
• And even as far back as 1984, a large outbreak in Swedish mink farms was found to be due to the H10N4 avian virus.

Mink are a member of the Mustelidae family of carnivorous mammals, which also includes otters, badgers, weasel, martens, ferrets, and wolverines. Many of these species are susceptible to flu viruses – most notably ferrets – which are often used in influenza research.

​

Over the past decade we've seen literally dozens of reports of spillovers into mink, including the generation of mink-variant COVID strains which - at least temporarily - circulated in humans in Europe back in 2020 (see Preprint: Emergence & Spread of SARS-CoV-2 Variants from Farmed Mink to Humans and Back - Denmark, June-November 2020)..​

Alarms were raised, again in the fall of 2022 when H5N1 began spreading rapidly through a large mink farm in Spain (see Eurosurveillance: HPAI A(H5N1) Virus Infection in Farmed Minks, Spain, October 2022).

​

This mink-derived H5N1 virus from Spain carried a rare mutation (PB-T271A), which is believed to `enhance the polymerase activity of influenza A viruses in mammalian host cells and mice'. In 2023 the CDC issued an IRAT Risk Assessment On Mink Variant of Avian H5N1, finding it's scores had risen in 6 of the 10 parameters used to evaluate their zoonotic potential.​

Spillovers into farmed animals are particularly worrisome, because they allow for serial transmission across a large number of hosts, which may result in host adaptation.

In 2023 we saw scores of fur farms (both mink & fox) in Finland hit by HPAI, resulting in massive culls.

During that protracted outbreak, in PNAS: Mink Farming Poses Risks for Future Viral Pandemics, we looked at an opinion piece by Professor Wendy Barclay & Tom Peacock on why fur farms - and mink farms in particular - are high risk venues for both flu and SARS.​

Since then, new studies have continued to highlight the risks, including last January's Zoonosis & Public Health: Detection of a Reassortant Swine- and Human-Origin H3N2 Influenza A Virus in Farmed Mink in British Columbia, Canada.

​

All of which brings us to a new study, published 3 days ago in the journal Viruses, which finds that (among a small cohort (n=37) of Chinese farmed mink) past LPAI H9N2 exposure was quite common (89.2%), while they found no detectable antibodies for human H1N1 or avian H3N2, H4N2, H5N1, H6N6, or H11N9.​

These pre-exposed mink, however, remained highly susceptible to other influenza A subtypes (only H1N1 and H6N6 were tested), raising concerns over the ability of mink to serve as `mixing vessels' for influenza reassortment.

​

While this study is subject to a number of limitations (cohort size, limited range of viral challenges, etc.), it provides additional evidence on the zoonotic risks of fur-farming; particularly involving mink.​

I've only posted the link, and a few excerpts. Follow the link to read the study in its entirety.

​

Replication and Transmission of Influenza A Virus in Farmed Mink​

​

Viruses 2026, 18(1), 9;https://doi.org/10.3390/v18010009 (registering DOI) This article belongs to the Special Issue Surveillance, Prevention, and Treatment of Avian Influenza​

Abstract​

​

Farmed mink are frequently exposed to circulating influenza A viruses (IAVs), as confirmed by viral isolation and serological evidence. Previous work reveals that naïve mink serve as susceptible hosts for both avian and human influenza strains, highlighting their potential role in influenza ecology.​

In this study, we investigated whether farmed mink naturally pre-exposed to H9 retain the capacity to serve as “mixing vessels” for reassorting human and avian IAVs. Our results demonstrate that they remain fully susceptible and permissive to infection by both avian H6N6 and human H1N1 influenza strains.​

​

Notably, efficient transmission of these viruses occurred among farmed mink, confirming their potential to sustain viral exchange. These findings indicate that farmed mink represent highly permissive hosts capable of facilitating reassortment between circulating human and avian IAVs.​

​

Given this risk, current mink farming practices may substantially increase the likelihood of a pandemic emergence. We therefore urge immediate revision, stringent enhancement, and rigorous enforcement of biosecurity protocols and active surveillance systems in fur farming operations.​

(SNIP)

​

4. Discussion​

​

Our study demonstrates that influenza-pre-exposed mink retain their capacity to serve as “mixing vessels” for avian and human influenza A viruses (IAVs), reinforcing the zoonotic risks associated with intensive mink farming.​

Despite serological evidence of frequent H9N2 exposure to farmed mink [1,19], these animals remained fully susceptible to heterosubtypic strains, including avian H6N6 and human-origin H1N1 viruses. Both strains replicated efficiently in the respiratory tract and exhibited sustained transmission among pre-exposed mink, confirming their potential to facilitate reassortment between avian and human IAVs.​

These findings parallel observations in swine, a well-documented mixing vessel, but highlight a critical gap in biosecurity oversight for mink farming, underscoring their role as underappreciated reservoirs for viral evolution.​

(Continue . . . .)

As we've discussed previously - while the next pandemic virus could certainly emerge directly from the wild - the practice of raising millions of highly (flu & COVID) susceptible animals in densely packed farms unnecessarily raises our pandemic risks.

​

While there is a growing movement to ban fur farms - particularly in the EU - Poland and Russia remain major fur producers, as well as the United States and Canada.​

China, however, remains the largest global producer and exporter of farmed fur, accounting for2/3rds of the world's mink farms.Reportedly fox and raccoon dogs are raised on many of these same farms, increasing the odds of inter-species transmission of novel viruses.

​

Whether we can summon the political will to take the necessary steps needed to prevent the next pandemic remains to be seen.​

But time is definitely not on our side.


https://afludiary.blogspot.com/2025/12/viruses-replication-and-transmission-of.html

 

[Michael Coston]

That Touch of Mink Flu (H5N1 in Utah Edition)

#19,305

Mink are members of the Mustelidae family of carnivorous mammals, which also includes otters, badgers, weasel, martens, ferrets, and wolverines. Many of these species are susceptible to flu viruses – most notably ferrets – which are often used in influenza research.

Over the past 20 years we've looked a a number of concerning spillovers, including:

• 2009's That Touch Of Mink Flu, where at least 11 mink farms in the Holstebro municipality of Denmark were reported to be infected with a variant of the human H3N2 virus.

• In 2007, an antigenically distinct H3N2 Swine Influenza was detected in Canadian Mink, reported in a 2009 Journal of Clinical Microbiology study called Characterization of a Canadian Mink H3N2 Influenza A Virus Isolate Genetically Related to Triple Reassortant Swine Influenza Virus.

• A year earlier CIDRAP reported on a European mink found infected with an aggressive form of the H5 flu virus in the Blekinge region of southern Sweden near where H5N1 had been detected in wild birds.

• And even as far back as 1984, a large outbreak in Swedish mink farms was found to be due to the H10N4 avian virus.

We've seen literally dozens of reports of spillovers into mink since, including the generation of mink-variant COVID strains which - at least temporarily - circulated in humans in Europe back in 2020 (see Preprint: Emergence & Spread of SARS-CoV-2 Variants from Farmed Mink to Humans and Back - Denmark, June-November 2020).

New alarms were raised in the fall of 2022 when H5N1 began spreading rapidly through a large mink farm in Spain (see Eurosurveillance: HPAI A(H5N1) Virus Infection in Farmed Minks, Spain, October 2022).

This mink-derived H5N1 virus from Spain carried a rare mutation (PB-T271A), which is believed to `enhance the polymerase activity of influenza A viruses in mammalian host cells and mice'. In 2023 the CDC issued an IRAT Risk Assessment On Mink Variant of Avian H5N1, finding it's scores had risen in 6 of the 10 parameters used to evaluate their zoonotic potential.​

In 2023 we saw scores of fur farms (both mink & fox) in Finland hit by HPAI, resulting in massive culls.

During that protracted outbreak, in PNAS: Mink Farming Poses Risks for Future Viral Pandemics, we looked at an opinion piece by Professor Wendy Barclay & Tom Peacock on why fur farms - and mink farms in particular - are high risk venues for both flu and SARS.​

Spillovers into farmed animals are particularly worrisome, because they allow for serial transmission across a large number of hosts, which may result in host adaptation.

Since then, new studies have continued to emerge highlighting the risks, including:

• January 2025's Zoonosis & Public Health: Detection of a Reassortant Swine- and Human-Origin H3N2 Influenza A Virus in Farmed Mink in British Columbia, Canada.

• Last December's Viruses: Replication and Transmission of Influenza A Virus in Farmed Mink

Yesterday the USDA updated their Detections of Highly Pathogenic Avian Influenza in Mammals dashboard to include 6 captive American Mink in Utah infected with EA H5N1 (see below).


1 To protect data confidentiality, the county and mapped locations of these detections represent the approximate location of the State capitol.

Details are extraordinarily scant (even the county location is `masked'), but the dates of collection and confirmation all are quite recent (8/7 & 8/17). This is presumably a fur farm, but no details are provided.

I've found no media reports on this event, and there appears to be nothing publicly available on theUtah Agriculture Department Website. As of this writing, I don't find anything on the WOAH WAHIS website, either.​

Whether these mink were sick, or died, or how many others might be infected on the premises or at risk, and what steps are being taken to contain this outbreak, or protect farm workers, isn't stated.

Utah has already been having a rough H5N1 summer, with 16 cattle herds reportedly infected since June, and nearly 1.5 million chickens culled due to the virus.​

There are disappointingly far too few details provided to make any reasonable assumptions about the size, or potential impact, of this outbreak. Hopefully we'll get more details sooner rather than later.

Note: After I posted this blog I noticed Hogvet51 has posted his own thoughts. If you aren't reading his substack, you should add it to your list.
​

https://afludiary.blogspot.com/2026/08/that-touch-of-mink-flu-h5n1-in-utah.html
​

 

[Michael Coston]

H5N1 in Utah Mink (Updated)​

#19,351

A little over a month ago, in That Touch of Mink Flu (H5N1 in Utah Edition), we looked at a cryptic report of an outbreak of H5N1 at a mink farm somewhere (exact location masked) in Utah.

The USDA Detections of Highly Pathogenic Avian Influenza in Mammals dashboard reported 7 captive American mink in Utah infected with EA H5N1 (see below).

1 To protect data confidentiality, the county and mapped locations of these detections represent the approximate location of the State capitol.

Other than this, I've found no other official local, state, or federal government statements posted online.

Thankfully, the The Animal Welfare Institute filed a Utah GRAMA public-records request with the Utah Department of Agriculture and Food (UDAF) on August 26, requesting all records concerning HPAI in American mink from June 1 onward.

On September 17th AWI published a 61-page UDAF GRAMA records release (PDF), along with a press release. Follow the link to read it in its entirety.

AWI Newsroom Press Statement

Records Request Reveals Unhurried, Inadequate Response to Bird Flu Outbreak in Utah Farmed Mink

Government records obtained by AWI highlight gaps in disease response protocol, the public health hazards of mink farming, and the urgent need to phase out the practice.

September 17, 2026

This 61-page GRAMA release consists principally of emails, text-message screenshots, internal correspondence, and one heavily redacted letter (dated Aug 26th) from UDAF to Agriculture Secretary Brooke Rollins.

Details, such as the size and location of the farm - and number of mink affected - are blacked out. No response from the Ag Secretary is included.

The UDAF qualifies their release by stating `Additional records, or portions thereof have been redacted or withheld because they contain information that is relevant to an ongoing investigation in accordance to Utah Code Ann. § 63G-2-305 (10)(a)'.

Yesterday (Sept 27th), the Salt Lake Tribune published a sobering report:

‘Watch them die’: Bird flu is ravaging a Utah mink farm, killing 80% of the herd. State agriculture officials have no clear plan.

It’s the first documented outbreak of bird flu in captive mink in the U.S., and an advocacy group is raising concerns about Utah’s response.

As we've discussed often, mink are particularly susceptible to influenza (and coronaviruses), and the way they are raised in captivity can permit the rapid spread - and evolution - of those viruses.

As an example, in the fall of 2022 H5N1 began spreading rapidly through a large mink farm in Spain (see Eurosurveillance: HPAI A(H5N1) Virus Infection in Farmed Minks, Spain, October 2022).

This mink-derived H5N1 virus from Spain carried a rare mutation (PB2-T271A), which is believed to `enhance the polymerase activity of influenza A viruses in mammalian host cells and mice'.

In 2023 the CDC issued an IRAT Risk Assessment On Mink Variant of Avian H5N1, finding its scores had risen in 6 of the 10 parameters used to evaluate their zoonotic potential.
Also in 2023, Finland's fur industry was hit unusually hard by HPAI H5N1, with more than 70 fur farms infected, and > 500,000 animals culled, prompting Finland's Institute for Health and Welfare (THL) to warn `Avian influenza poses a risk to public health – improvements to health security needed at fur farms'.

During the height of this outbreak, we looked at an excellent opinion piece (see PNAS: Mink Farming Poses Risks for Future Viral Pandemics) penned by two well known virologists from the UK (Professor Wendy Barclay & Tom Peacock) on why fur farms - and mink farms in particular - are high-risk venues for flu.

Since then we've seen several other notable outbreaks, including a reassorted swine and human-origin H3N2 in Canadian farmed mink. Many farms, and governments, remain reluctant to provide details on outbreaks, and so we are likely only seeing the tip of the iceberg.

Earlier this month, in The Lancet Regional Health Europe (Comment): If the EU is serious about One Health, it must ban fur farming, we looked at yet another call to action.

Meanwhile, events such as the one in Utah, continue to occur. Perhaps, given the reluctance to report, more often than we know.

And contrary to the old saying, what we don't know can hurt us.


https://afludiary.blogspot.com/2026/09/h5n1-in-utah-mink-updated.html