Glasgow Warriors' Pro14 meeting with Edinburgh on 27 December has been postponed after at least four positive Covid-19 tests in the Glasgow squad.
Warriors' European Champions Cup match against Lyon on Saturday had already been cancelled.
Twenty Glasgow players were forced to isolate after a coronavirus outbreak at last weekend's Champions Cup opponents Exeter Chiefs, who won 42-0.
Four Warriors players subsequently returned positive tests.
And the club are awaiting the results of a further round of testing, but their 2 January meeting with Edinburgh is not affected as things stand.
"Glasgow Warriors have consulted, and sought the support of, Scottish Rugby's Threat Management Group over the postponement of the game," Warriors said in a statement.
"In addition, having considered all the available evidence, the Pro14 Rugby Medical Advisory Group has deemed that this fixture cannot go ahead as scheduled.
"Pro14 Rugby will examine potential dates in early 2021 to reschedule the game."