Friday's Super League game between Huddersfield Giants and Castleford Tigers has been cancelled due to 12 coronavirus cases in the latter's camp.
Castleford revealed on Wednesday they had returned a number of positive results, having undergone testing on Tuesday.
The Tigers lost 28-24 to Leeds Rhinos on Monday and the possibility of their opponents having contracted the virus is now to be explored.
A statement read: "The RFL [Rugby Football League] and Super League will today liaise with Public Health England, Castleford Tigers and the Tigers' last opponents, Leeds Rhinos, before the multiple case group meets to consider the data and decide next steps.
"Super League and the RFL are actively exploring all options and will make a further announcement as soon as practicable."
Ninth-placed Castleford cannot qualify for the play-offs, having won just 37.5 per cent of their games, but both Huddersfield (seventh with 43.75 per cent) and Leeds (fifth with 60 per cent) are still in contention for a top-four finish.
With Warrington Wolves' clash with Salford Red Devils also being called off later in the day, Huddersfield will now face the Wire at the Totally Wicked Stadium on Friday.