Leicester's European Challenge Cup tie with Castres has been cancelled after three of the French side's players tested positive for coronavirus.
Tigers will go straight into the semi-finals after medical advice saw Castres have to forfeit Sunday's quarter-final.
A member of the visitors' staff tested positive, as well as the three players.
"The decision followed a meeting of a medical committee, comprising medical leads from the unions, league bodies and both clubs," European Rugby said.
"The committee, chaired by Rod McKenzie (Scotland), met by video conference last night following confirmation by Castres that three members of their playing group, as well as one staff member, had tested positive for Covid-19 in advance of the club's planned departure to England."
A Leicester statement added: "It is disappointing to reach this position after all of the hard work put into restarting fixtures in the professional game across Europe, but safety and wellbeing must come first.
"We wish a full and speedy recovery to anyone affected at Castres Olympique and send them our best wishes for the rest of the season."
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