Thursday, November 12, 2020

ECDC Rapid Risk Assessment: Detection of New SARS-CoV-2 Variants Related to Mink

Credit ECDC


Just over a week ago, in Denmark Orders Culling Of All Mink Following Discovery Of Mutated Coronavirus, the world learned of a potentially dangerous mutation in the SARS-CoV-2 virus that emerged from infected mink, and has been transmitted on to at least 12 humans. 

Mutation reports are often over-hyped by the media, and should be taken with a grain of salt. Most of the time they prove less problematic than expected.  Sometimes, however, they can exceed expectations, and so a cautious approach is justified. 

The Danish government quickly ordered the culling of as many as 17 million mink (which was reversed 2 days ago, pending legislation), locked down North Jutland, and issued strong warnings about the risks posted by this mutation (see  Risk assessment from the Statens Serum Institut).

Since then, we've seen a Risk Assessment from the World Health Organization - that while lengthy - posed more questions than answers. On Saturday, the ECDC announced their intentions of producing a Risk Assessment by today, Nov. 12th. 

Within the past hour the ECDC has published their initial assessment which is based on limited data - and while quite detailed - is limited in what conclusions it can draw. 

Risk assessments of newly emerging threats are apt to change as more data is collected, and generally deal with current risks, not risks going forward.  First a link and excepts from the Executive Summary, followed by some selected excerpts from the 19-page Risk Assessment.  

You'll want to download and read the full document. 
Rapid Risk Assessment: Detection of new SARS-CoV-2 variants related to mink
Risk assessment
12 Nov 2020 
This assessment considers the risk to human health posed by SARS-CoV-2 mink related variants. It is based on information available to ECDC at the time of publication and, unless otherwise stated, the assessment of risk refers to the risk that existed at the time of writing.
It follows the ECDC rapid risk assessment methodology, with relevant adaptations. The overall risk is determined by a combination of the probability of an event occurring and its consequences (impact) for individuals or the population.

Executive summary

Since April 2020, when the first SARS-CoV-2 infection was reported in the Netherlands in a mink and subsequently in a mink farm worker, it has been established that human-to-mink and mink-to-human transmission can occur. Since then, infections in mink have been reported in Denmark, Italy, Spain, Sweden and the United States.

On 5 November 2020, Denmark reported 214 human COVID-19 cases infected with SARS-CoV-2 virus variants related to mink, as well as infected mink at more than 200 mink farms. Most human and animal cases reported since June 2020 have been in the North Jutland Region. The SARS-CoV-2 variants detected in these cases were part of at least five closely-related clusters; each cluster was characterised by a specific mink-related variant, identified in humans and animals from infected mink farms. Denmark has implemented robust response measures to control the outbreaks in mink and decrease the spill-over between the human and the animal reservoir.

One of the clusters (Cluster 5), which was reported as circulating in August and September 2020, is related to a variant with four genetic changes, three substitutions and one deletion, in the spike (S) protein. Since the S protein contains the receptor-binding domain, and is a major target for immune response, such mutations could, in theory, have implications for viral fitness (ability to infect humans and animals), transmissibility, and antigenicity. 

As a consequence, the evolution of viruses with increasing changes in functional domains of the S protein could affect treatment, certain diagnostic tests and virus antigenicity. It could also have an impact on the effectiveness of developed vaccine candidates, and possibly require them to be updated.
Investigations and studies are ongoing to clarify the extent of these possible implications.
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Open file in new window - EN - [PDF-521.73 KB]

I've reproduced the section on the risk assessment to human health below.


What is the risk to human health posed by SARS-CoV-2 mink related variants?


Current evidence available from Denmark and the Netherlands on SARS-CoV-2 variants related to mink indicates that these variants are able to circulate rapidly in mink farms and the human communities close to the farms, however, they do not appear to be more transmissible than other circulating SARS-CoV-2 variants. Thus, the probability of infection with mink-related variant strains is assessed as low for the general population, moderate for populations in areas with a high concentration of mink farms and very high for individuals with occupational exposure.


Patients reported to be infected with mink-related variants, including the Cluster 5 variant in Denmark, do not appear to have more severe clinical symptoms than those infected with non-mink-related variants. Therefore the current impact of COVID-19 on disease severity in patients infected with any mink-related variant appears to be similar to those infected with non-mink-related variants. This impact was previously assessed as low for the general population and very high for individuals with risk factors for severe COVID-19 disease, such as the elderly.

Immunity, reinfection, vaccination and treatment

Of all mink-related variants analysed so far, only the Cluster 5 variant has raised specific concern due to its effect on antigenicity. Further investigations are needed to assess whether this may have any impact on i) the risk of reinfection, ii) reduced vaccine efficacy or iii) reduced benefit of treatment with plasma from convalescent patients or with monoclonal antibodies. It should be noted that continued transmission of SARS-CoV-2 in mink farms may eventually give rise to other variants of concern.

Cross-border spread

The cross-border spread of SARS-CoV-2 variants related to mink in EU/EEA countries and the UK through humans has not been observed so far, but there is no indication that the potential for cross-border spread is different to that for other SARS-CoV-2 variants. Genetic adaptation in mink populations could give rise to a selective advantage in regions with mink farming activity. The mutation Y453F, defining mink-related variants, has also been detected outside of Europe, indicating the potential for circulation of such strains. In the past few months, community transmission has occurred in Denmark and, to some extent, in the Netherlands, which could lead to cross-border spread.

The cross-border spread of SARS-CoV-2 variants related to mink in EU/EEA countries and the UK through animals and animal products appears very low.


Based on the information currently available on transmissibility, severity, immunity and cross-border spread, the overall level of risk to human health posed by SARS-CoV-2 mink-related variants can be determined as:

low for the general population and moderate for medically-vulnerable individuals, which is no different to other SARS-CoV-2 strains (not related to mink);

low for the general population in areas with a high concentration of mink farms and moderate-to-high for medically-vulnerable individuals living in the same areas;

moderate for non-medically vulnerable individuals with occupational exposure and very high for medically vulnerable individuals with occupational exposure.

If the concerns raised in relation to immunity, reinfection, vaccination and treatment are confirmed, the risk assessment will be immediately reviewed to re-assess the overall level of risk to human health and the potential implications for COVID-19 diagnosis, treatment and vaccine development. This also applies to any further mink related variants with mutations in the S protein that may arise and spread in the EU/EEA and the UK.

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