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Mink farms’ coronavirus outbreak driven by workers

Covid-19 transmission between mink farms in the Netherlands was associated with movements of staff, study suggests.

Map showing coronavirus clusters in the Netherlands.
Scientists identified five coronavirus clusters, each representing a separate introduction of the virus into farms.

Workers such as farmers and drivers were largely responsible for coronavirus spread between mink farms during an outbreak that affected more than half of farms in the Netherlands, scientists have found.

Cats, dogs and wild animals such as badgers living around mink farms could also have spread coronavirus between farms during the outbreak between April and November 2020, the findings suggest.

The approach used in the study, combining genetic and virus distribution information, could help understand behaviour of this and other viruses that spread between people and animals.

Genetic insights

Scientists analysed the genetic makeup of coronavirus from infected minks and farm workers in 64 out of 68 infected farms. They sought to investigate the timing of virus introduction into different farms and how the virus spread from farm to farm.

They compared the rate at which the virus mutated when spreading between farms with the mutation rate in the wider population.

The analysis revealed five virus clusters, each representing a separate introduction of the virus into farms, with the first happening in April 2020. They found that a mutation in the largest cluster led to faster evolution, wider and longer spread of the virus than in the other clusters, affecting 40 farms across 15 municipalities.

Scientists identified farms from which the virus was most likely to have spread by quantifying transmission patterns.

Farms near infected farms were more likely to be infected than those further away, the study reports.

The virus jumped back and forth between minks and humans on several farms, but spread from mink farms back into local communities was limited, scientists concluded.

The study, led by the University of Edinburgh’s Usher Institute, involved scientists from the Roslin Institute and organisations in the Netherlands. It was funded by the European Union’s Horizon 2020 programme through the Versatile Emerging infectious disease Observatory (VEO) project. The findings are published in Nature Communications.

Preventing outbreaks

Fur farming was banned in the Netherlands from January 2021 and no further cases in minks have been reported.

Continuous surveillance and implementation of preventive measures in fur farms and other susceptible animals could reduce virus spread, scientists suggest.

Combining data from the virus genome with information on virus evolution helped us understand how coronavirus spread between mink farms. This approach could be used to understand and predict outbreaks of this and other viruses.

Dr Samantha LycettThe Roslin Institute

There is a risk that infected animals become virus reservoirs that can infect humans in the future. It is fundamental to keep monitoring the situation and to prevent the virus from being reintroduced into mink farms and spread to humans.

Dr Lu LuUsher Institute

** The Roslin Institute receives strategic investment funding from the Biotechnology and Biological Sciences Research Council and it is part of the University of Edinburgh’s Royal (Dick) School of Veterinary Studies. **

Related links

Scientific publication

Roslin Covid-19 research

VEO project