There are fears this year's Tour de France could be disrupted by Covid-19 after an outbreak hit this week's Tour de Suisse, one of the final major warm-up races.
With two weeks to go to the opening stage of the Tour in Copenhagen, 29 riders did not take the start of Friday's stage six in Switzerland, including overnight race leader Aleksandr Vlasov and Britain's Olympic mountain bike champion Tom Pidcock, after 16 riders quit on Thursday.
Three teams - UAE Team Emirates, Alpecin-Fenix and Bahrain-Victorious - pulled out entirely following positive cases, while EF Education-EasyPost withdrew four riders including Rigoberto Uran and Hugh Carthy.
Vlasov and his Bora-Hansgrohe team-mate Anton Palzer pulled out as well as Israel Premier-Tech's Reto Hollenstein and Sebastian Barwick, Trek-Segafredo's Gianluca Brambilla, Movistar's Alex Aranburu, and QuickStep-Alpha Vinyl's Louis Vervaeke, leaving 94 starters.
Pidcock became the second member of the Ineos Grenadiers squad to withdraw after Adam Yates on Thursday. Geraint Thomas remains in the race and sits second overall, one second behind Israel Premier-Tech's Jakob Fuglsang, after Team DSM's Nico Denz won Friday's mountainous stage from a breakaway.
Following a meeting involving teams, rider representatives and governing body the UCI, Tour de Suisse race director Olivier Senn said the remaining 18 teams had agreed to continue but admitted there was no guarantee the race would reach Vaduz on Sunday.
"It's obviously not nice," Senn said. "We've very sad that coronavirus is spreading so far within the teams. All the teams know the rules. Four teams decided to withdraw including the one yesterday so there's 18 teams.
"All the remaining teams agreed to start and there is no further decision on today's stage. We will reassess tomorrow morning and obviously we hope we don't have many more cases. In the moment we keep going as planned."
UAE Team Emirates also reported Mikkel Bjerg had tested positive at the Tour of Slovenia and had been withdrawn along with roommate Vegard Stake Laengen.
However the rest of the team, led by reigning Tour de France champion and this year's favourite Tadej Pogacar, will continue.
