The Giro d'Italia is on the brink of cancellation after five teams were hit by Covid-19 cases on the first rest day, with two of them pulling out of the three-week grand tour 12 days before the finish in Milan.
The Australian Mitchelton-Scott team withdrew after four staff members tested positive for the coronavirus following top rider Simon Yates pulling out last week. Jumbo-Visma, whose leader Steven Kruisjwijk tested positive, did not start today's 10th stage.
A Team Sunweb rider, one staff member from Ineos-Grenadiers and AG2R-La Mondiale also returned positive tests, organisers RCS said.
RCS, in a joint statement with the International Cycling Union, said the teams' doctors had ordered "isolation measures".
Sunweb's Michael Matthews had tested positive and sports director Luke Roberts said the Australian was asymptomatic.
"Obviously it's really disappointing to lose one of the riders," Roberts told reporters. "We're in with a fight for the GC (General Classification) and Michael was and would have been a great help to us.
"Nevertheless, that's bike racing and we'll continue to chase after our goals and I hope we can make it to Milan."
Jumbo-Visma said they had pulled out of the race for the safety of everyone involved.
"We thought it was the most responsible decision because we've all been close to Steven," sports director Addy Engels said.
Mitchelton-Scott said the team were notified of the four positive results for staff members from tests done on Sunday.
"Unfortunately, we received the news on Monday evening that we have returned a number of positive Covid-19 results to members of our staff after our third round of tests in three days," the team's general manager Brent Copeland said.
"As a social responsibility to our riders and staff, the peloton and the race organisation we have made the clear decision to withdraw from the Giro d'Italia.
"Thankfully, those impacted remain asymptomatic or with mild symptoms."
Yates, who like Kruijswijk had been among the pre-race favourites, withdrew on Saturday after testing positive for the virus.
Kruijswijk was 11th overall, 1:24 behind race leader Joao Almeida of Portugal and 27 seconds behind double champion and fifth-placed Vincenzo Nibali of Italy.
Riders in the Giro stay in a biosecure bubble when not on the road as they did for the Tour de France, which finished on 20 September. Four staff members but no riders tested positive for the virus that causes Covid-19 while on the French tour.
On the Tour de France, two positive tests in a team within one week would have triggered the ejection of the outfit from the race but no such rule was put in place for the Italian grand tour, which started in Sicily on 3 October.
Dutchman Jos van Emden of Jumbo-Visma criticised the organisation, saying the bubble was not secure enough.
"The other day we were in there with four or five teams... but in that particular hotel we were in, the neutral service, the police on motorbikes were there, just normal people were there and they were all eating from the same buffet so I think it was a real big mistake," Van Emden told The Cycling Podcast.
"I heard from a guy from (Deceuninck) Quick Step they had exactly the same, this guy sent me a movie from their dining hall and also Mitchelton-Scott were there... for me there's no doubt were he (Simon Yates) got the virus."
Italy, which hosted the rescheduled world championships last month, has seen a recent rise in coronavirus cases, with a post-lockdown record 5456 people infected registered last Saturday.
Elite racing resumed in August after a four-and-a-half month hiatus.
However, the resurgence of Covid-19 in Europe has forced local authorities and organisers to cancel races, such as the Netherlands' Amstel Gold Race, which had been scheduled for Saturday, and Paris-Roubaix, the "Monument" classic that was due to be raced on 25 October.
-Reuters