The Guinness PRO14 round 8 fixture between the Scarlets and Leinster, the reigning champions and current Conference A leaders, has been postponed.
The game was due to take place this Sunday in Llanelli, however, a small number of Scarlets players have returned positive cases of Covid-19 and others identified as close contacts are now isolating.
Having considered all of the available evidence, the PRO14 Rugby Medical Advisory Group has deemed that this match cannot go ahead as scheduled.
Ulster, who played against the Scarlets in Belfast last Sunday, carried out routine squad testing today and will receive their results in the next 24 hours.
PRO14 Rugby will examine potential dates in early 2021 to reschedule the Scarlets v Leinster game.