Leeds Rhinos have closed their training ground for five days to act as a "fire break" after six players and one member of staff tested positive for Covid-19 in the last 10 days.
The Betfred Super League club says those affected are isolating at home for a minimum of 10 days and players and staff will have to produce a negative test before they are allowed to return.
All players and staff will also have daily lateral flow tests while the training ground is closed.
The Kirkstall base, which was virtually destroyed by floods six years ago but survived their latest downpour, will undergo a scheduled full deep clean this week while the players and staff are off-site.
In line with Government guidelines, the club says Public Health England has been informed.
Leeds director of rugby Kevin Sinfield said: "Firstly, I would like to thank our players and staff for how they have adhered to the guidelines and rules in place since we returned to training.
"We are in a privileged position as an elite sport that we can continue to train. With that privilege comes a great deal of responsibility.
"Whilst this may be a short disruption to our pre-season plans, it is important that we look after the wellbeing of our people, their families, and the local community.
"We have increased our bio-security from last season and everyone is vigilant about ensuring we lessen the probabilities of spreading the virus.
"Because of our increased testing since New Year, it has become evident that, despite all our precautions, the virus has continued to spread within the group.
"We hope this short period will act as a fire break and enable us to move forward next week."
The start of the 2021 Betfred Super League season has been put back two weeks to March 25 due to lockdown restrictions.
Fitzpatrick 'incredibly proud' of rugby league
Warrington Wolves CEO Karl Fitzpatrick has told Sky Sports he is "incredibly proud" of all associated with the sport of rugby league, for how they have handled the impact of Covid-19.
Speaking exclusively as a guest on this week's Golden Podcast episode, Fitzpatrick paid tribute to the sport in the wake of news the Super League season has been delayed by two weeks to March 25.
"It's been absolutely incredible," Fitzpatrick told Sky Sports. "The hurdles, the challenges, that have been continually thrown at the game.
"However I'm so proud to be involved in rugby league, because the adaptability, the nimbleness, the ability to basically do whatever it takes to ensure the game has a future and survive has been incredible.
"And that's right through the players. When the rest of the world was social distancing and staying apart - and continuing to do so - the players have been going into battle, grappling, wrestling, tackling each other. Doing all that on reduced pay as well.
"It's been simply remarkable.
"Then you look at the governing body, and they are dealing with the situation fantastically well. They managed to secure a loan from the government before any other sport.
"Then you look at Super League, who have been the driving force behind putting games on. Changing fixtures, rescheduling the season, and as you are aware we have just announced we are moving the season back slightly. And again that just shows how adaptable the sport is, and you need to be in these times.
"I am so proud of the sport and what we are doing at the moment. And I am very confident due to the willingness, the attitude of the players, staff, RL and Super League, that we will come out the other side."