Leicester's Challenge Cup quarter-final at home to Castres has been cancelled due to cases of coronavirus at the French club.
Three of Castres' players and one other member of staff tested positive for Covid-19 ahead of their planned departure to England, European Professional Club Rugby said.
With Castres having to forfeit the tie, which had been set to take place at Welford Road on Sunday, Leicester advance to the semi-finals.
EPCR said its decision followed a meeting of a medical committee on Friday comprising medical leads from the unions, league bodies and both clubs, and subsequent independent medical advice.
A message on Leicester's official Twitter feed said: "Not the way we wanted to progress to the next stage of the @ERChallengeCup... Most importantly, we wish our friends at @CastresRugby all the best at this time and look forward to our next meeting with them - whenever it may be... Onto the next challenge, whoever it is against!"