Future Tense

How a Coronavirus Mutation in Minks Could Wreak Havoc on Vaccine Development

White minks in cages
Minks on a farm in Herning, Denmark. Ole Jensen/Getty Images

Update, Nov. 10, 2020: Since the writing of this piece, the Danish government has reversed its decision to euthanize all minks in the country after farmers and members of the opposition party expressed concerns about the legality, necessity, and economic impact of the slaughter. Although mink-to-human transmission of COVID-19 is still ongoing in Denmark and surrounding nations, more than one month has passed since researchers have detected an infection caused by the mutated strain. Animal rights groups, including Humane Society International, continue to voice support for the now-discarded measure.

Officials in Denmark announced Wednesday that they would be euthanizing every last mink in the country’s fur farms, some 17 million animals. The news came after a discovery by Danish scientists that SARS-CoV-2, the official name for the virus that causes COVID-19, had mutated in captive minks, producing a strain of the coronavirus that is not readily stopped by antibodies to the dominant strain of the virus. More troublingly, this new strain is still transmissible from minks to humans, raising dire concerns about the efficacy of vaccines currently in development worldwide.

There are currently five reported cases of the new strain in minks and 12 cases in humans, all workers at one of the roughly 1,100 mink farms in Denmark. Although the humans are being monitored, isolated, and treated in keeping with recommendations from public health officials, the minks are not so lucky—mass extermination is already underway. More than 400 mink farms have already culled the entirety of their mink populations, likely by gassing them. Police and military personnel are being deployed to destroy all minks on the remaining farms as soon as possible. According to Finnish fur auctioneer Magnus Ljung, pelts from minks near infected farms are unfit for sale and will be destroyed, almost half the total count. The remaining pelts will be sold as less valuable summer pelts. All told, extermination of the minks will cost an estimated $785 million.

Since the beginning of the pandemic, more than 50 animal species have tested positive for the dominant strain of SARS-CoV-2. When news broke in April that several domestic dogs and cats had tested positive, there were no calls for mass euthanasia of house pets. Spread to wild animals—tigers, bats, and great apes to name a few—has also been documented, but at no point did epidemiologists recommend such dramatic intervention to stop the spread in those species, several of which are endangered. The case of the Danish minks, however, is different. Other animal species that have caught the coronavirus from people were infected with the dominant strain of the virus, the one that’s been making headlines for the better part of the past year. Additionally, most of those species turned out to be dead-end hosts for the virus, meaning that although the virus could infect those animals, and even cause disease in those animals, the virus was unable to turn around and jump from animal to human, a phenomenon called zoonosis.

Minks are an exception to this rule. The European mink industry has been battling outbreaks of the dominant strain of COVID on farms since June, after a rash of COVID-19 cases in people in northern Denmark was ultimately traced back to those farms. Once it became clear that the animals themselves were the source of the infections, minks were slaughtered en masse on farms where these outbreaks had taken place. The Netherlands culled more than 10,000 after coronavirus outbreaks this summer. Officials in Spain slaughtered almost 10 times as many after an outbreak occurred at a farm in the Aragón province. Those minks were contracting and spreading the dominant strain of the coronavirus, the one we all know and dread.

The development this week is the discovery that minks in Denmark are now testing positive for a mutant strain of the virus that is not readily destroyed by COVID antibodies. Experts warn that if the outbreak of this mutant strain is not sufficiently contained, the world could be facing a second pandemic.

So how did the mutation happen? Every organism on the planet mutates. When the genetic code is getting copied, errors occur frequently. When a letter in the genome is inadvertently replaced with a different letter, that is called a mutation. The vast majority of mutations are either inconsequential or cause harm to the organism. Rarely, though, a mutation will actually empower the organism—in this case, the virus.

Coronaviruses as a general rule mutate slowly compared with other viruses. Take, for instance, the seasonal flu. Because influenza viruses can shuffle their genetic code like a deck of cards, battling the flu with seasonal vaccines is perpetually frustrating; some years the efficacy of the flu vaccine is as low as 10 percent. By the time researchers can develop a more effective vaccine, the flu has mutated again, often rendering the previous year’s vaccine useless. Because studies confirmed that SARS-CoV-2 was not undergoing significant mutations as it spread from person to person, researchers were optimistic in the early stages of the pandemic that a vaccine would confer long-lasting protection, unlike the flu vaccine.

However, SARS-CoV-2 has mutated before. Back in May, there was a small panic about a coronavirus mutation that seemed to increase the virus’s transmissibility, or the ease with which it passes from one person to another, thanks to a modification in a spike protein on its surface. The fears later proved unfounded, spread by nonscientists over-interpreting the paper after it was discussed in publicly accessible online forums prior to peer review. Fortunately, researchers were later able to confirm that this mutation did not represent a paradigm shift in our response to the virus, nor would the mutation affect vaccine development; antibodies made against viral strains with the spike protein mutation were still able to destroy the previous, unmutated version of the virus.

The virus produced by the mink mutation, on the other hand, seems impervious to antibodies produced in response to the dominant strain of the virus. What makes this mutation so much more troubling than previous mutations is not that the mutation increases how quickly the virus will spread, nor that it increases the severity of resultant disease. It’s the fact that the immune system cannot transfer knowledge about one form of the virus in fighting the other form. From the perspective of your immune system, they are two different viruses altogether.

In other words, if you have survived COVID-19, your immune system remains largely unequipped to battle the mink strain. Once pharmaceutical companies finish their monthslong race to devise an effective COVID vaccine, the vaccine would likely provide little protection against the emerging strain. The virus has mutated into what could eventually be thought of as COVID 2.0 if the Danes fail to contain its spread.

Kåre Mølbak, who directs the Danish government’s public health and infectious disease arm, summed it up when he told Reuters on Wednesday, “The worst-case scenario is a new pandemic, starting all over again out of Denmark.”

There is, fortunately, some cause for cautious optimism here. First, we don’t know yet how the mutant strain will affect the human body clinically. The 12 people infected with the mink strain may all remain symptom-free if the mink mutation also happens to have lowered its ability to cause disease. For all we know, the mutation could just as easily result in a virus that is even better at killing people than the current virus. We simply don’t have enough information.

The second silver lining is the low case count of this mutant coronavirus—currently 12 people and just five animals. Given the rapid, aggressive governmental response, there is a good chance that this mutation will be stamped out before it can spread significantly, at least in the mink population. What hangs in the balance is the fate of the 12 infected people whose current health status remains unknown. Were they asymptomatic for a time? Did they have contact with friends and family prior to diagnosis? Will they spread it to health care workers treating them? Barring the hope for an impotent strain of the virus, it’s not hard to imagine a scenario in which cases of the mink strain explode exponentially, similar to the course of the original virus.

As our twin COVID-19 battles of public health and public resistance rage on in the U.S., the laudable response by officials in Europe stands in stark contrast to the response here. Wearing face covers, socially distancing, washing our hands frequently, and quarantining when appropriate are all we can do as individuals. But the governmental response—contact tracing, free and speedy testing, a health care system that won’t obliterate you with medical debt—is every bit as important. Fortunately for the world, the mink mutation didn’t happen here.

Update, Nov. 7, 2020: This article was updated to include information about what will happen to the pelts of the exterminated minks.

Future Tense is a partnership of Slate, New America, and Arizona State University that examines emerging technologies, public policy, and society.