Powell was forced to scrap training on Wednesday and Leeds coach Richard Agar says his club’s preparations were also disrupted.
Three players from the Rhinos’ last opponents, Wigan, have tested positive this week and Agar was forced to hastily put back Wednesday’s captain’s run by an hour as he waited for re-tests after some initial ones proved inconclusive.
“Thankfully everybody has been cleared,” said Agar.
Wigan will go ahead with Friday’s game against Warrington and Powell says it is crucial clubs play to a conclusion this season.
“I think it’s really important that we get through the season,” he said. “It’s going to be tough.
“Obviously the Challenge Cup final is in a couple of weeks’ time, so that will be one of the competitions that come to a conclusion and then it’s getting through the rest of it and getting the Grand Final played.
“We’ve just got to act tough. To scrap the season would be disastrous, I’d hate to see that.
“We’ve got to battle through. Rugby league is a tough sport played by tough people from generally working-class areas where they want to see this, they want to see sport.
“As difficult as it is, we have to get through. I just don’t think we should be thinking about quitting. We don’t quit in rugby league, we crack on as much as we can until it’s an impossible situation.
“It may come to that, I don’t know, but until there is no other option, I think we need to keep going.”