SARS-CoV-2 strain variant associated with mink – Denmark

As of June 2020, 214 cases of COVID-19 have been identified in Denmark in humans with SARS-CoV-2 variants associated with farmed mink, including 12 cases with a unique variant, reported on 5 November. All 12 cases were identified in September 2020 in North Jutland, Denmark. The cases ranged in age from 7 to 79, and eight were related to the mink breeding industry, and four cases were from the local community.

Initial observations suggest that the clinical presentation, severity, and transmission of the infected are similar to those of other circulating SARS-CoV-2 viruses. However, this variant, called the “cluster 5” variant, had a combination of mutations or changes not previously observed. The implications of the identified changes in this variant are not yet well understood. Preliminary findings suggest that this specific variant associated with mink, identified in both females and in 12 human cases, has a moderately reduced sensitivity to neutralizing antibodies. Further scientific and laboratory testing is needed to verify the reported preliminary findings and to understand the possible implications of this finding in terms of diagnosis, therapy, and vaccines in development. Meanwhile, the Danish authorities are taking action to limit the further spread of this variant of the virus among mink and human populations.

SARS-CoV-2, the virus that causes COVID-19, was first identified in humans in December 2019. As of November 6, it has affected more than 48 million people causing over 1.2 million deaths worldwide. Although the virus is believed to be ancestrally related to bats, the origin of the virus and the middle host (s) of SARS-CoV-2 have not yet been identified.

Available evidence suggests that the virus is mainly transmitted to humans through respiratory droplets and close contact, but there are also examples of transmission between humans and animals. Several animals that have been in contact with infected people, such as minks, dogs, domestic cats, lions and tigers, have tested positive for SARS-CoV-2.

Minks are infected after exposure to infected people. Minks can act as a reservoir of SARS-CoV-2, transmitting the virus to each other and pose a risk for the virus to spread from the mink to humans. Humans can then transmit this virus within the human population. In addition, spillovers (human-to-mink transmission) may occur. It remains a concern when any animal virus is transmitted to the human population or when the animal population could contribute to the intensification and spread of a virus that affects humans. As viruses move between the human and animal populations, genetic modifications of the virus can occur. These changes can be identified by sequencing the entire genome, and once found, experiments can study the possible implications of these changes on disease in humans.

To date, six countries, namely Denmark, the Netherlands, Spain, Sweden, Italy and the United States, have reported SARS-CoV-2 in farmed minks to the World Organization for Animal Health (OIE).

Public health response

The Danish authorities have announced the following planned or permanent public health actions:

• Excretion of all farmed martens (more than 17 million) in Denmark, including farms;
• Strengthen local surveillance to detect all cases of COVID-19, including mass PCR testing for the entire population for the North Jutland region;
• Increasing the percentage of sequencing of SARS-CoV-2 infections in humans and mink in Denmark;
• Rapid division of full genome sequences of the SARS-CoV-2 mink variant; and
• Introduction of new movement restrictions and other public health measures to the affected areas in North Jutland to reduce further transmission, including movement restrictions between municipalities.

WHO risk assessment

All viruses, including SARS-CoV-2, change over time. SARS-CoV-2 strains that infect mink, and which are then transmitted to humans, may have acquired unique combinations of mutations. Advanced laboratory studies are needed to fully understand the impact of specific mutations. This research takes time and is conducted in close collaboration with different research groups.

Recent findings reported by the Danish Public Health Authority (Statens Serum Institut) in Denmark regarding a new version of SARS-CoV-2 identified in humans need to be confirmed and further assessed to better understand all possible transmission implications, clinical presentation , diagnosis, therapy and vaccine development.

Furthermore, detailed analyzes and scientific studies are needed to better understand the reported mutations. Sharing the full genome sequences of human and animal strains will continue to facilitate detailed analyzes by partners. Members of the WHO SARS-CoV-2 Virus Evolution Working Group are working with Danish scientists to better understand the available results and collaborate on further studies. Further scientific and laboratory testing will be undertaken to understand the implications of these viruses in terms of available diagnostics, therapy, and vaccines against SARS-CoV-2.

The action of the Danish authorities will limit the continued proliferation of mink-related versions of SARS-CoV-2 in Denmark, and they have been specifically implemented to contain a unique variant reported to the WHO. These actions include restricting the movement of people, shooting animals, extensive testing of people living in the affected areas, and enhanced genomic sequencing of the SARS-CoV-2 virus across the country.

WHO advice

This event highlights the important role that mink populations can play in the continuous transmission of SARS-CoV-2 and the critical role of strong surveillance, sampling and sequencing of SARS-CoV-2, especially around areas where such reservoirs have been identified.

Denmark’s preliminary findings are globally relevant and the WHO recognizes the importance of sharing epidemiological, virological and whole genome data with other countries and research teams, including through open source platforms.

The WHO advises that further virological tests should be conducted to understand the specific mutations described by Denmark and to further investigate any epidemiological changes in the function of the virus in terms of its transmissibility and the severity of the disease it causes. The WHO advises all countries to increase the order of SARS-CoV-2 viruses, where possible, and to share order data internationally.

The WHO advises all countries to step up surveillance of COVID-19 at the animal-human interface where sensitive reservoirs for animals, including mink farms, have been identified.

The WHO also reminds countries to strengthen biosecurity and biosecurity measures in agriculture around known animal reservoirs 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 could be involved in livestock or animal shooting.

The basic principles for reducing the general risk of transmission of acute respiratory infections are as follows:

• Avoiding close contact with people suffering from acute respiratory infections;
• Ensuring frequent hand washing, especially after direct contact with sick people or their surroundings;
• For people with symptoms of an acute respiratory infection, practicing cough etiquette, such as maintaining distance, covering coughs, and sneezing with disposable wipes or clothing and washing hands; use masks as needed; and
• Improving standard infection prevention and control practices in hospitals in health facilities, especially in emergency departments.

The WHO has issued guidelines for Public health considerations during the continuation of international travel, recommending a thorough risk assessment, taking into account the country context, local epidemiology and transmission patterns, national health and social measures to control outbreaks and the capacity of health systems in countries of departure and destination, including at points of entry. In case of symptoms indicating acute respiratory illness during or after the trip, travelers are advised to seek medical attention and share their travel history with their doctor. Health authorities should work with the travel, transport and tourism sectors to provide passengers with information on reducing the overall risk of acute respiratory infections through travel health clinics, travel agencies, carriers and entry points.

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