Thomas Barr has been forced to pull out of the World Athletics Championships due to gastroenteritis.
The Ferrybank athlete was due to run in tonight's 400 metres hurdles semi-finals at the London Stadium, but the 2016 Olympic finalist has withdrawn after contracting the vomiting bug.
The bitterly disappointed Waterford man said: "I'm gutted to have to withdraw from today's semi final. I wasn't feeling great yesterday evening and later in the night I was hit with a bad bout of gastroenteritis.
"My whole year has been focused on the World Championships. The support yesterday was just brilliant and to not be able to go out and compete today for Ireland is beyond disappointing."
Barr's absence means there will be no Irish athletes in action on Day 4 of the Championships, where the highlights include the finals of the men's 110m hurdles and the women's 1500m.
Barr reported that he was feeling unwell several hours after his qualification run from the heats of the 400 metres hurdles yesterday.
He had been noticably short of his trademark strong finish as he moved off the final two hurdles but blamed that on a change of 'lead leg' in his hurdling technique.
Then at 2am this morning, he took ill with a vomiting bug, later diagnosed as gastroenteritis, and he had no option other than to withdraw from tonight's semi-final in which he had been drawn in lane 9 in the same race as Olympic champion Kerron Clements.
Barr has had to be isolated in a room on his own at the team hotel near Tower Bridge after he was examined by doctors, effectively quarantined from other athletes staying there..