Officials in the Netherlands say mink passed COVID-19 to two farm workers.
They are probably the first such cases, they said.
Testing identified mink infected with COVID-19 on four of 155 farms subsequently tested, Agriculture Minister Carola Schouten said in a letter to parliament.
She said the risk of such animal-to-human transmission of the virus outside the farms was “negligible.”
On three of the four infected farms, the source of virus infecting the mink has been shown to be a sick human, while the fourth is still under investigation, the minister said.
The Netherlands’ Institute for Health’s (RIVM) director Jaap van Dissel said that, while a few cats and other animals had been infected with COVID-19 by humans, the Dutch mink-to-human transmissions were practically unique.