For athletes at the Beijing Winter Olympics, testing positive for Covid-19 is one of their worst nightmares, and it can begin with a knock on the door in the middle of the night.

“It was insane, it was a rollercoaster,” said Kim Meylemans, a skeleton racer from Belgium.

The 25-year-old posted a tearful video on Instagram last week from isolation which highlighted the perils of competing in the middle of a pandemic, AP reports.

It is unclear how many of the nearly 3,000 athletes in Beijing have tested positive, but there have been 429 Covid-19 cases in the “closed loop” bubble in which the competitors and about 65,000 others are cocooned.