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So you may have heard concerns about the mink variant of #SARSCoV2 that was discovered in Denmark and is leading to the decision to cull all farmed minks in the country.
This should not be a cause for panic. https://www.nytimes.com/2020/11/04/health/covid-mink-mutation.html
This should not be a cause for panic. https://www.nytimes.com/2020/11/04/health/covid-mink-mutation.html
This is another example of sharing data by press release, and on its face, it sounds alarming:
-People got infected with it
-People mounted weak antibody responses
-Danish public health official said that this strain would interfere with vaccine efficacy
OH NO SOUNDS BAD
-People got infected with it
-People mounted weak antibody responses
-Danish public health official said that this strain would interfere with vaccine efficacy
OH NO SOUNDS BAD
There is no data available to support any of these statements so it's hard to evaluate them. However, we know a few other things that may mitigate concerns a bit.
In the Netherlands, there were big mink farm outbreaks earlier this year. https://www.reuters.com/article/us-health-coronavirus-netherlands/netherlands-to-close-mink-farms-after-coronavirus-outbreaks-idUSKBN25N2W2
In the Netherlands, there were big mink farm outbreaks earlier this year. https://www.reuters.com/article/us-health-coronavirus-netherlands/netherlands-to-close-mink-farms-after-coronavirus-outbreaks-idUSKBN25N2W2
The Dutch mink farms were likely the result of anthroponotic transmission (from humans to minks). At least 2 people are thought to have then contracted SARS-CoV-2 zoonotically (from minks to humans). So it's not surprising that there were cases in Denmark. https://www.nationalgeographic.com/animals/2020/11/denmark-mink-culling/
Ferrets, which are related to minks, are used as an experimental model of COVID-19 (well, more like a model of SARS-CoV-2 infection, because ferrets don't get very sick). So it's not shocking that minks are susceptible to infection.
So far there have not been any data demonstrating that COVID-19 caused by mink-derived variants is substantially different from human-derived variants. "Weak" antibody responses are seen in mild or asymptomatic COVID-19 cases too.
Now let's get to the most worrisome claim, that the mink-derived viruses will render vaccines less effective. This suggests that replication in the mink selected for mutations in critical regions of SARS-CoV-2 antigens, probably the spike protein.
However, without knowing what those mutations are, it's unclear what the implications are for vaccines. Unless the mutations are in regions of spike (called neutralizing epitopes) that are important for antibody neutralization, that's just speculation.
Even if there are mutations in known neutralizing epitopes, it's still speculation. You can use all the fancy computational and structural modeling tricks in your toolbox to predict the functional effect of a mutation but you won't actually know until you test it experimentally.
And furthermore, RNA viruses like SARS-CoV-2 are always mutating. It's normal and expected. We already know that any mutation, whether from a human- or mink-derived variant, can occur in an important epitope.
Mutations are changes in the RNA genome. When these occur in a part of the genome that encodes a viral protein, it can result in a different amino acid being inserted in that protein than the amino acid that was originally encoded. That can affect antibody binding to that epitope
Antibodies are exquisitely specific and sometimes even a single amino acid substitution can abrogate antibody binding. Thus a mutation in a key epitope could mean that vaccines raised against one variant will elicit antibodies that don't protect against variants w/ the mutation.
But they haven't shown what mutations the mink-derived variants have acquired, so who knows? Mutations arise in human-derived viruses too, so the moral of the story is that we need to conduct robust surveillance for all circulating SARS-CoV-2 isolates to look for escape variants.
So there's no reason to be extra concerned about these mink variants without evidence otherwise. We should review the data objectively when available and we should continue and expand genomic surveillance.
The thing I'm most concerned about was not really addressed by the Danish authorities: spillback into a new reservoir species. If SARS-CoV-2 starts circulating in wild animals, then we risk future outbreaks caused by zoonotic transmission from exposure to these new reservoirs.
I'm already very concerned that SARS-CoV-2 could become established in cats. Cats are susceptible to infection and there are millions of feral cats in the US (and millions more globally). If cats become an established reservoir, we may be stuck with SARS-CoV-2 for years to come.
In this regard, it's good that the Dutch mink industry is shutting down entirely by 2021. Hopefully other countries will follow suit. Mink farming is also unnecessary and cruel, so there's little upside for continuing the practice if it's also a spillback risk.
But I really wish that the trend of science by press release would stop. There's no reason why the genomic data couldn't be shared, which would allow the scientific community to evaluate these claims. It's hard to communicate risk when you haven't seen the data.
ADDENDUM: Yes I know the difference between Dutch and Danish. When I said the Dutch mink industry is shutting down by 2021, I was referring to mink farming in the Netherlands. It's not clear to me that mink farming in Denmark is ending for good after the animals are culled.
