South African 400 metres world record holder Wayde van Niekerk has tested positive for COVID-19 while training at his European residence in Gemona in Italy.
It now means he will have to quarantine and therefore will miss an athletics meeting in Trieste today, per La Gazzetta dello Sport.
He intended to run the 100m and the 400m.
In the Olympic final at Rio 2016, Van Niekerk ran the fastest time in history - 43.03sec.
His time broke the previous record of American sprinting legend Michael Johnson, who posted 43.18 in the 400m final at the 1999 World Championships in Seville in Spain.
Van Niekerk is the most high-profile figure in athletics to contract the virus to date and this is a blow to the 28-year-old who injured himself in 2017 in a charity rugby game.
Since tearing his anterior cruciate ligament in the match, the South African has suffered further setbacks and only returned to action in the early track season prior to the COVID-19 pandemic.
In that time, he competed in two consecutive weeks - both at events in Bloemfontein - running respectable times of 10.10 for the 100m and 20.31 in the 200m.
The following week, on February 29, he returned to the 400m with a time of 47.42 - more than four seconds down on his world record.
Van Niekerk only recently arrived in Genoma alongside African long jump champion Ruswahl Samaai and African 110m hurdles champion and record holder Antonio Alkana.
Sprint coach Tannie Ans Botha and long jump coach Jenny Kingwill also travelled to Italy.
South African sprinter and Commonwealth Games 100m champion Akani Simbine was expected to join them this month, along with his coach Werner Prinsloo, but that plan could be in peril.
Van Niekerk figures to be one of the biggest draws at the Tokyo 2020 Olympics and now has the advantage of another year of preparation.
He was the first man in history to run under 10 seconds in the 100m, 20 seconds in the 200m and 44 seconds in the 400m.