It means the Welsh club’s match against Benetton, which was scheduled to take place on Saturday night, has been cancelled.
Under Pro14 Rugby protocols, the game is deemed a 0-0 draw, but four match points are awarded to the team who had not been the cause of the postponement, meaning Benetton are now uncatchable at the top of the Rainbow Cup standings.
The Italian side will go through to the final against the leading side in the South African Rainbow Cup competition. Vodacom Bulls are the currently top of the standings.
The final will take place on June 19 at Benetton’s Stadio di Monigo in Treviso.
Glasgow lost to Benetton in their opening Rainbow Cup match but then won the next four and went to the top of the table on Friday night after beating Pro14 champions Leinster.
However, it was their final group match and they were relying on Benetton and Munster failing to win their final games this weekend.
There were three positive cases in the Ospreys squad
A statement from Pro14 Rugby said: “Ospreys Rugby are working closely with Public Health Wales following the latest round of Covid-19 testing at the club, which returned 3 positive results.
“The decision to cancel the game is a result of the mandate from Public Health Wales that all individuals who were part of the travelling party from the previous fixture are now required to self-isolate in-line with public health protocols.
“With no available weekends remaining, the game will not be rescheduled. As a result, PRO14 rugby will use the protocol decided prior to the 2020/21 season whereby a game that could not be rescheduled would result in that fixture deemed a 0-0 draw, but four match points would be awarded to the team who had not been the cause of the postponement.
“In this case, Benetton will receive four match points. This protocol ensures that no artificial scoring points were added to the tries/points for and against columns.
“Adding four points to Benetton’s current total of 18 will provide the Italian team with a final standing of 22 points. It is mathematically impossible for any other team in the table to win more than 20 points, therefore Benetton Rugby will be the ‘Northern’ representative in the Guinness PRO14 Rainbow Cup Final on Saturday, June 19.”