Olympic and world 3,000m steeplechase champion Conseslus Kipruto will miss the first Diamond League event of the season in Monaco after testing positive for coronavirus.
Kipruto, 25, had been one of 11 Kenyan athletes cleared to compete on 14 August after the French government waived their visa applications.
But he announced he had failed the Covid-19 protocol test on Saturday.
"I don't have any symptoms and I was actually in great shape," he said.
"I was planning to go for the world record - it has stayed too long outside Kenya."
Kipruto claimed gold at the Rio 2016 Olympics and won back-to-back world titles at London in 2017 and Doha last year.
He has a personal best of eight minutes 00.12 seconds, with Kenyan-born Qatar athlete Saif Saaeed Shaheen holding the current men's world record of 7:53.63.
"I wish to thank Monaco for all the work they have done and I wish them and my colleagues a wonderful competition," added Kipruto.
"Athletics is back and I will be back as well."
Following exhibition events in Oslo and Zurich in June and July, Monaco will mark the start of the competitive season.
A further six events, including an exhibition street event in Lausanne, are currently scheduled to take place this year, after meetings in Eugene, London, Paris, Rabat, Gateshead and Shanghai were all cancelled because of coronavirus.