Trek-Segafredo, the team of 2019 world champion Mads Pedersen and Milan-San Remo winner Jasper Stuyven, withdrew from the Gent-Wevelgem on Saturday after a Covid-19 outbreak.

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Pascal Ackermann and his Bora-Hansgrohe were also not on the start line, prevented by the organizer because it reportedly deemed some riders and staff high-risk. Its rider Matthew Walls did not race the E3 BinckBank Classic after testing positive for Covid.

"One team member tested positive for Coronavirus on Friday. They were then put into isolation along with the other team members who had been in close contact with them," said a team statement on the eve of the race.

"The entire team underwent an extra PCR test which revealed a positive result for one of the isolated members.

"The team has decided to withdraw from Gent-Wevelgem whilst we do further testing before we can safely return to competition."

Pedersen was also the defending champion in Sunday's race which will take place over a 254km course.

German cycling team Bora say they are angry after becoming the second team to miss out on Sunday's big race in Belgium due to Covid.

Bora followed Trek-Segafredo into the quarantine bay, but while Trek went voluntarily, a doctor's ruling excluded Bora from the Gent-Wevelgem classic, who had wanted to take part.

"I am very disappointed and angry," said Bora manager Ralph Denk.

"A GP from the region can block an entire team in one of the largest one-day races in the world."

The decision was made by the doctor at a previous race from Friday, the E3 Saxo Bank Classic.

Denk accepted that one of his riders had tested positive and that he and his room-mate should have been excluded, but not the entire team.

Race organisers told Bora on Sunday morning of the news that 17 people in their team had been designated as "high risk contact" and placed under a seven-day quarantine in a country staggering under a wave of Covid infections.

Denk said his team were taking tests every day, and would have preferred to have been trusted.

"The part of the team that has been quarantined will be quarantined until April 1," he said.

"This also means that we cannot start at Dwars Door Vlaanderen."

Gent-Wevelgem officials said it was "not up to an organiser like ourselves to judge whether the quarantine is fair or not."

Trek-Segafredo chose to withdraw under similar circumstances with one rider testing positive.

"The team has decided to withdraw from Gent-Wevelgem whilst we do further testing before we can safely return to competition," the team said.