Dutch scientists are closely investigating a case where a human appears to have been infected with Covid-19 from a mink, a small semi-aquatic mammal farmed for its soft fur. The claim remains unconfirmed for now, but the unusual case could be the first confirmed instance of animal-to-human transmission of Covid-19 during the pandemic.
In April, several minks at two mink fur farms in the Netherlands appeared to be infected with Covid-19 after a number of animals developed a severe respiratory disease, according to an announcement by the Dutch government. At both farms, at least one worker had tested positive for SARS-CoV-2. During their investigation into the outbreak, researchers led by Wageningen University carried out a genetic analysis of the pathogens to build up a “family tree” of the virus.
This research revealed that one worker at a mink farm had contracted an extremely similar form to some of the animals. It appears that a human first brought the infection into the farm, but the genetic variations of the virus suggest it's likely that one worker was actually infected by the mink. The researchers also noticed that viral RNA was found in the inhalable sawdust used as bedding in the mink houses, indicating the possible route of exposure to workers.
The research, which has not yet been peer-reviewed, is available on the preprint server bioRxiv.
Obviously, it’s not every day you run into a mink, though the two extant species lives near the rivers of North America and Europe, so the Dutch National Institute for Public Health and the Environment has said the risk of the virus being transmitted from minks to humans outside fur farms is “negligible.” However, the country’s agriculture minister and health minister are looking to introduce new measures on mink farms in light of the outbreak.
Covid-19 is a zoonotic disease that originated in animals before jumping to humans. Scientists aren't yet certain which animal species SARS-CoV-2, the coronavirus that causes Covid-19, stemmed from, but bats are considered the most likely candidate so far. There is also some evidence that humans can pass on the disease to other animals, such as pet dogs or even tigers. However, as yet, there has not been a confirmed case of a specific animal species transmitting the virus to humans.
That is still the case for now, as scientists still need to confirm and clarify the findings from the mink farm outbreaks. Nevertheless, independent experts have verified that the claims of the Dutch researchers are well-founded.
“The detailed analyses of the viruses from the mink and the human that the Dutch scientists and authorities have presented gives me confidence that this suggestion is justified and supported by evidence,” Professor James Wood, Head of Department of Veterinary Medicine at the University of Cambridge in the UK, told IFLScience.
“When you have a cluster of animal cases, human exposure will increase – and so this sole factor increases the likelihood of such a thing happening – it is quite different to just having contact with a single cat, for example," Professor Wood explained.
"This is the only ‘reverse-zoonosis’ example I am aware of during this pandemic.”