The novel coronavirus appears to have been introduced to Danish mink farms by a single infected person, but once it got into the densely packed animals it spread fast, Danish researchers reported Wednesday.
The virus doesn’t make the animals very sick but can circulate well among them and they can then pass it back to people, the researchers said.
“A high proportion of mink on farms can be infected with SARS-CoV-2 within a few days, which may provide major virus exposure to persons working with mink,” Anne Sofie Hammer, a veterinary pathologist at the University of Copenhagen, and colleagues wrote in the journal Emerging Infectious Diseases.
Silent spread: Hammer's team tested mink and people at three Danish mink farms, as well as the air around the cages and the minks' feed. They found 95% of the mink at one farm were infected, 66% of the mink at the second farm were infected and 3% of the mink at the third farm were.
“The infections we describe here occurred with little clinical disease or increase in death, making it difficult to detect the spread of infection; thus, mink farms could represent a serious, unrecognized animal reservoir for SARS-CoV-2,” they wrote.
“There is no evidence for spread of the virus outside of farm buildings, either in Denmark or in the Netherlands except by infected persons. However, there appears to be some risk of virus transmission to persons working with infected mink as well as for their contacts and thus, indirectly, for the public.”
Coronavirus outbreaks on mink farms have caused an uproar in Denmark, where farming the animals for their fur is big business. The government ordered a cull of all 15 million mink on 1,500 farms, then rolled back the order.