He had been feeling lethargic and took a positive test yesterday. Instead of altitude training in Italy, it will now be recovery and rest at home in Östersund.
The world number one long-distance skier is trying to look at it positively.
"I'd rather take it now than in January or February, and it doesn't feel like it's going to sink me," says Persson, who has had COVID once before.
Then he was away from training for a week and another week before he was in good shape.
The 28-year-old hopes to be able to compete in the premiere of Ski Classics in Bad Gastein on December 9, but without much expectation. Last season, he won nine races.
"It's a bit of a smouldering place, but if I can start training again, maybe on Sunday, I can probably go down and do it as the first race, but maybe not hope for any result. I can't hope for any good results before Christmas but after Christmas it probably won't affect me that much.
The infection probably came from his teammate in Lager 157, Oskar Kardin, with whom he shared a room.
"Hopefully it's just us who are affected, I haven't heard of any others," Persson said.
The team also includes the 17-year-old super talent Alvar Myhlback.