A competitor in Alaska's annual Iditarod Trail Sled Dog Race has tested positive for coronavirus.
Gunnar Johnson was withdrawn from the 832-mile (1,339km) event under tight pandemic restrictions.
Officials described the 52-year-old - who is competing in his third Iditarod - as "incredibly disappointed".
Known as the "Last Great Race on Earth", the Iditarod involves teams of dogs controlled by mushers racing across the Alaskan wilderness.
While the race usually covers the distance from Anchorage in the south of the state to Nome in the north - a 938-mile journey - authorities this year have altered the course.
The 2021 event, which started on Sunday, will see racers go in a loop from the town of Willow, north of Anchorage, to the abandoned town of Iditarod, before returning again to Willow.
Competitors must also practice social distancing and wear face masks. Only 47 mushers entered this year due to the restrictions.
Johnson is not the first to withdraw from the gruelling race. Aliy Zirkle was forced to cut her effort short after suffering an injury two days into the event. Organisers said she suffered a concussion following a "significant impact" somewhere on the trail.