The impact of the virus on teams is going to be massive.
Tottenham are out of the Europa Conference League after UEFA ruled they forfeited their final match against Rennes.
The match on December 9 was called off following a Covid outbreak, with 13 positive cases at the London club.
UEFA then said the match could not be rescheduled and referred the matter to its disciplinary body.
It awarded Rennes a 3-0 win and they top the group, with Vitesse runners-up and Spurs finishing third.
While the Conference League isn't Europe's highest honor, it's still a European competition that teams will want to win. And the money that comes with it is very lucrative. Covid outbreaks are now threatening that revenue stream, which is bound to become a bigger story.
"We are disappointed by the ruling of the UEFA Appeals Body and the refusal to allow more time for the match to be rescheduled," Spurs said.
"We have to accept this ruling, however, and our focus now turns to the competitions we remain in."
Following the outbreak, Spurs were forced to close their first-team training center, with their subsequent Premier League games against Brighton and Leicester also postponed.
The game against Rennes was Spurs' final game in Group C of the Europa Conference League.
Eight Spurs players and five members of staff tested positive for Covid-19. UEFA rules state that if clubs have 13 fit players on their A list, including a goalkeeper, they must play.