London Irish's Premiership game at Bath on Boxing Day is off after Exiles players test positive for Covid-19.
A league statement said "a small number" of players were found to have the virus and the game was postponed after another presented with symptoms.
Saturday's game between Newcastle and Leicester was called off on Tuesday after an outbreak in the Tigers squad.
London Irish boss Declan Kidney said the club was "incredibly disappointed" their game could not go ahead.
The director of rugby said that his players had "acted professionally, following all the relevant guidelines".
"But this is the situation we find ourselves in at the moment, as the country continues to try and navigate its way through the pandemic," Kidney continued.
The postponement is the second for Bath in the past week, with their Heineken Champions Cup fixture with La Rochelle called off after Covid-19 outbreaks.
That decision came as Bath had 12 players isolating after a positive test was returned by Scarlets, who the English club were beaten by in the European competition a week earlier.
Bath said that they would have been "able to safely field" a side against Irish on Saturday.
Bath's director of rugby Stuart Hooper said the club "stand by" all fellow Premiership sides and that "the health and safety of everyone in our sport must be our top priority".
"I know this news will be hard felt by our supporters who were due to attend and, but I know you'll understand and join me in wishing all those affected this week a full and safe recovery," Hooper continued.
The allocation of points for the match will now be decided by a league panel.
Premiership regulations state that "the team responsible" for the cancellation are awarded two points, while "the team that wasn't" pick up four.