At least 66 fur farm workers and their family members have been infected with coronavirus, scientists say in an investigation into the outbreak of Covid-19 at 16 Dutch fur farms up to the beginning of June.

In a number of cases, the virus has been passed from mink to humans, the scientists say in an preliminary article on scientific website biorxiv.org. Farm minister Carola Schouten said earlier that the risk of animal to human transmission was not great, even though two cases were confirmed at the start of the outbreak.

The team used genome sequencing to trace the spread of the virus between mink, cats and humans and found that 66 people and 11 cats all had a ‘mink variety’ of the virus.

In one case, they found that the virus had been introduced by an infected worker, but in most cases it was hard to establish how the virus had spread. There is no evidence of airborne infection because neighbouring farms had different varieties of the virus, the scientists say.

Nor did the researchers find any evidence that people living near fur farms are at risk.

Nevertheless, the virus has spread so far in mink that virologist Marion Koopmans told the Volkskrant that she could not rule out fur trade having a role in the spread of the virus to humans in China.

‘It could be a plausible point in the route which virus has followed as it moved from bats to humans,’ she told the paper. ‘This could be one of the links we are still missing.’