Minks farmed for their fur are acquiring SARS-CoV-2 from humans and transmitting it back, a classic scenario for possible genetic mutation that could create a mismatch with vaccines under development, the World Health Organization (WHO) reports.
“Since June 2020, 214 human cases of COVID-19 have been identified in Denmark with SARS-CoV-2 variants associated with farmed minks, including 12 cases with a unique variant, reported on 5 November,” WHO stated.1 “All 12 cases were identified in September 2020 in North Jutland, Denmark. The cases ranged in people ages 7 to 79 years. Eight had a link to the mink farming industry and four cases were from the local community.”
Although the clinical presentation in humans was similar to other COVID-19 infections, WHO reported a so-called “cluster 5” variant that had a combination of previously unobserved mutations.
“Preliminary findings indicate that this particular mink-associated variant identified in both minks and the12 human cases has moderately decreased sensitivity to neutralizing antibodies,” WHO reported. “Further scientific and laboratory-based studies are required to verify preliminary findings reported and to understand any potential implications of this finding in terms of diagnostics, therapeutics, and vaccines in development.”
To head off the threat, Danish officials are culling more than 17 million farmed mink and will conduct mass polymerase chain-reaction (PCR) testing of the human population in the Jutland area.
They also are increasing surveillance of the local population to detect all COVID-19 cases, including through population-wide mass PCR testing for the region of North Jutland.
They also will conduct genetic sequencing of human and mink SARS-CoV-2 to identify the mutated strain. Mitigation efforts include limiting transportation and movement between Jutland and other cities.
“Minks were infected following exposure from infected humans,” WHO reported. “Minks can act as a reservoir of SARS-CoV-2, passing the virus between them, and pose a risk for virus spill-over from mink to humans. People can then transmit this virus within the human population. Additionally, spill-back (human to mink transmission) can occur.”
At the time of this report, Denmark, the Netherlands, Spain, Sweden, Italy, and the United States have reported SARS-CoV-2 in farmed minks.
Although the general scientific consensus is that epidemic coronaviruses arise from bats, the original severe acute respiratory syndrome (SARS) in 2002 found an intermediate host in palm civet “cats” sold at Chinese wet markets.
Similarly, Middle East respiratory syndrome (MERS) has established a reservoir in camels. Palm civets were aggressively culled, and SARS disappeared. The first MERS cases emerged in 2012 and the link to dromedary camels is now well-established. Because of their central cultural role in the region, camels have not been culled and MERS still spreads sporadically.
Finding SARS-CoV-2 in minks and, to a lesser extent, in other animals raises the possibility that coronavirus eventually will become endemic through an animal reservoir.
“The question is going to be, can we ever truly eradicate SARS-CoV-2 from the human population?” Michael Ryan, MD, MPH, director of the health emergencies program at WHO, said recently at the IDWeek 2020 meeting. “That’s going to be a tough one.”
Rather than eradication, the goal should be reining in the virus via vaccines, therapies, and other public health measures, he added.
“If health systems can recover, maybe we can reach a point where this virus may enter the pantheon of all those viruses that can affect us from time to time, but we have the therapeutics and we absolutely have control over what it does to us,” Ryan said. “If we get there, I will consider that to be a public health success. Then we will decide whether we can eradicate this disease or not.”
Given the current situation, WHO recommended detailed analyses and scientific studies to better understand the reported mutations. The WHO made several other key recommendations in the report.
- The sharing of full genome sequences of human and animal strains will continue to facilitate detailed analyses by partners.
- This event highlights the important role that farmed mink populations can play in the ongoing transmission of SARS-CoV-2 and the critical role of strong surveillance, sampling, and sequencing SARS-CoV-2, especially around areas where such animal reservoirs are identified.
- The preliminary findings by Denmark are globally relevant and WHO recognizes the importance of sharing epidemiological, virological, and full genome sequence information with other countries and research teams, including through open-source platforms.
- All countries should enhance surveillance for COVID-19 at the animal-human interface where susceptible animal reservoirs are identified, including mink farms.
- Farming biosafety and biosecurity measures around known animal reservoirs should be strengthened to limit the risk of zoonotic events associated with SARS-CoV-2. This includes infection prevention and control measures for animal workers, farm visitors, and those who may be involved in animal husbandry or culling.
- WHO advises against the application of any travel or trade restrictions for Denmark based on the information currently available on this event.
- World Health Organization. SARS-CoV-2 mink-associated variant strain – Denmark. Disease Outbreak News. Nov. 6, 2020. https://www.who.int/csr/don/06-november-2020-mink-associated-sars-cov2-denmark/en/