A new report suggests that January’s Sundance film festival, the annual gathering of cinephiles in Park City, Utah, may have been a key early hub for coronavirus in the US. The article, in the Hollywood Reporter, cites numerous attendees who experienced Covid-19-like symptoms either during or immediately after the festival. None were believed to have been tested for the disease.

Sundance this year attracted about 120,000 people to the small mountain resort, to watch films and party in confined spaces. The snowy conditions that make Park City perfect for skiing mean that socialising indoors is common, as are some flu-like symptoms as a result of the low temperature and high altitude.

Yet this year’s “Sundance plague” appears to have been more virulent for regular attendees than earlier iterations, with many complaining of considerable difficulties breathing, multiple trips to hospital and at least a fortnight bedbound.

The Hollywood Reporter cites – but declines to name – one major actor who apparently became “gravely ill” after the festival, as did members of his entourage. They quote the Black List founder Franklin Leonard saying he became sick on 28 January, when he flew home to LA. Shortly after, he says, “I was barely functional … as sick as I’ve ever been for two weeks.” Leonard reports that at least two others he knew of cut their festival trip short due to illness.

A spokesperson for the Sundance festival said: “We’re sorry to hear that any of our festival attendees were unwell either during or after our January edition. We are not aware of any confirmed festival-connected cases of Covid-19.”

The Hollywood Reporter quotes a microbiologist, Dan Hart, who flags the fact the festival began on the same day as the lockdown in Wuhan. “Logic dictates that [sick attendees] most probably did have it. With Sundance, you’ve got the perfect formula for this virus to really go to town and contaminate everybody.”

The article’s thesis has been defended by festival-goers on social media who have been sharing their own stories of post-Sundance illness.