Titleholders Exeter's European Champions Cup clash with Toulouse on Sunday has been cancelled after several players and staff tested positive for coronavirus, organisers announced on Wednesday.
Glasgow - who Exeter crushed 42-0 in their opening pool match last weekend - have also called off their home game with Toulouse's fellow French side Lyon on Saturday as many of their players are self-isolating as a result of the Chiefs news.
"EPCR (European Professional Club Rugby) has been informed that a number of Exeter Chiefs players and staff have tested positive for COVID-19," read an EPCR statement.
"In accordance with public health guidelines, the club will not be able to send a match day squad to fulfil its Champions Cup, Round 2 fixture against Toulouse at Stade Ernest Wallon on Sunday (20 December).
"The Pool B match is therefore cancelled."
The EPCR said that Glasgow felt compelled to cancel their game as they would be unable to select a competitive side.
"Glasgow Warriors have advised EPCR that many of its senior players are now self-isolating in accordance with public health guidelines," read the statement.
"Consequently, the club is not in a position to field a match day squad of the appropriate standard for its Champions Cup, Round 2 fixture against Lyon at Scotstoun Stadium on Saturday (19 December).
"The Pool B match between Glasgow Warriors and Lyon is therefore also cancelled."
The EPCR added it will convene Match Result Resolution Committees to determine the results of the cancelled matches and the decisions of the committees will be communicated as soon as practicable.