(CNN)Dutch authorities believe a mink may have infected a human with Covid-19, and are instituting mandatory testing at all mink farms in the Netherlands.
"On the basis of new research results from the ongoing research into Covid-19 infections at mink farms, it is plausible that an infection took place from mink to human," the Dutch government said in a statement late Tuesday night.
"It also appears from this research that minks can have Covid-19 without displaying symptoms."
The government said antibody testing of minks would be expanded to "all mink farms in the Netherlands and will become mandatory."
The government also said it believes cats may be playing a role in the spread of the virus between farms. "Ongoing research shows the viruses at two of the infected farms are very similar," the statement said. Covid-19 was found in three out of 11 cats at one mink farm, it said.
"In the course of this investigation, it is advised that infected mink farms ensure that cats cannot enter or leave the farm premises."
World Health Organization spokesperson Fadela Chaib said last month that all available evidence says Covid-19 originated in bats, but experts have previously warned against drawing conclusions about other animals transmitting the virus to humans.
At least eight big cats have tested positive for the virus at Bronx Zoo.