Hull FC and Salford Red Devils will not be involved in Super League fixtures this weekend after six Hull players tested positive for Covid-19.
The fixture schedule for Saturday and Sunday has been rejigged, with all matches still taking place behind closed doors at St Helens.
All tests undertaken by Salford players have come back negative, but 11 Red Devils players have been told to self-isolate by the club.
The Rugby Football League's analysis of Sunday's match showed those 11 came into prolonged contact with infected Hull players - face-to-face contact of several seconds - and are therefore at increased risk of contracting the virus.
Saturday's game between Salford and Catalans will not go ahead, nor will Hull's fixture with Castleford on Sunday, while Hull's Challenge Cup sixth-round tie against Castleford on 22 August is also in serious doubt.
The revised fixture list for 15-16 August is as follows:
- Saturday, 16:15 BST: Wakefield Trinity v Catalans Dragons
- Saturday, 18:30 BST: Huddersfield Giants v Warrington Wolves
- Sunday, 16:15 BST: St Helens v Castleford Tigers
- Sunday, 18:30 BST: Wigan Warriors v Leeds Rhinos
Super League executive chairman Robert Elstone said: "Throughout this crisis our priority has been to ensure we minimise any risk, and the postponement of this weekend's scheduled fixtures involving Hull FC and Salford underlines that approach.
"It left us with another challenging situation, but it is a credit to the solidarity of the Super League clubs who agreed to adjust the fixture list at such short notice."
Meanwhile, Hull owner Adam Pearson has told BBC Radio Humberside that one potential source of infection at his club could have come from an unnamed player having to take his sick child to hospital.
The player is reported to have been sent home from training after displaying symptoms of Covid-19.
Pearson, whose diabetes leaves him at risk as an underlying medical condition, said the health and welfare of players affected and their families is the primary concern despite the sporting impact.
"We've locked down and are going through the track and trace process and taking things are detailed and intensively as we can to make sure it doesn't spread any further," he continued.
"That's the most important thing now, they're fit young boys, it's not so much the players. You worry about the people in and around them in their families.
"Everybody is in isolation now at home within their own family environment, but the family environment is different from player to player."
Pearson added: "Some have more vulnerable children than others, some players are more worried than others and some symptoms are stronger than others.
"All players are at home, have been stood down from training and won't return to training for seven to 10 days before they even consider.
"There will need to be a series of tests done to make sure we're all clear."