We know humans can give SARS-CoV-2 to animals. But can animals give it to humans?

Since the pandemic began, pet owners have worried that their pets could catch COVID, yet there have been fewer than 50 cases of cats and dogs contracting SARS-CoV-2 in the US, and no documented cases of infected pets passing the virus to humans.

The jury’s still out. But a new study published this month in the journal Science by researchers in the Netherlands indicates that at least one animal is capable of infecting humans with the novel coronavirus: minks.

They made headlines last April when several mink farms in the Netherlands reported outbreaks of the coronavirus in the animals. Similar outbreaks followed in Denmark and Spain, which resulted in the culling of more than a million minks. Last August, an outbreak was reported on several mink farms in Utah, though reportedly no culling took place.

Dutch researchers were on it by May, when preliminary genetic analysis suggested that minks on one Dutch farm may have caught the virus from humans and then passed it back to two farmworkers, in what the researchers called the world’s first “plausible” reports of animal-to-human transmission.

In the new study, which seems to confirm that early analysis, the researchers used whole-genome sequencing of SARS-CoV-2 outbreaks on 16 Dutch mink farms to reveal virus transmission from human to mink, and also from mink to human.

Their analysis combined SARS-CoV-2 diagnostics, whole-genome sequencing, and in-depth interviews with farmworkers. By the end of June, 66 of 97 workers at the mink farms had tested positive for SARS-CoV-2.

That analysis also revealed that some of the infected humans were infected with virus strains with an animal sequence signature, providing evidence of animal-to-human transmission.

NEWStat reached out to study coauthor Wim H. M. van der Poel, DVM, PhD, DECVM, a zoonotic virology expert at Wageningen University in the Netherlands, to find out more.

Van der Poel told NEWStat that he and his colleagues sequenced virus samples taken from infected minks as wells as virus samples taken from infected farmworkers who worked with the minks. “In the “There were infections in humans before and after the outbreak in the minks,” he said. By comparing the sequences, the researchers were able to show that the virus was introduced to the minks by infected workers.

The presence of a genetic animal signature in samples from workers who got sick a few weeks after the initial outbreak also showed that those workers were infected by minks—not by other humans.

Van der Poel stressed the importance of genetic sequencing in their research: “First, to track the origins of the virus, and now, to look into variants and their dynamics and virulence.”

He said that by dating the sequences and subsequent mutations, they were able to determine that there were five separate introductions of the virus to minks on a handful of farms, and the virus spread from there: “In total, 70 farms were infected and have been culled.” Van Der Poel said mink farming in the Netherlands ceased completely by the end of 2020.

NEWStat asked Van der Poel how his research related to infection of companion animals.

“Cats and dogs can be infected with SARS-CoV-2,” he said, noting that dogs and cats who lived on the mink farms also tested positive for SARS-CoV-2 but that “the cats and dogs hardly showed clinical signs.”

“To date, there’s no evidence that [infected pets] contribute to virus spread in the human population,” he added.

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