The Strade Bianchi, the first big race of the Italian cycling season, was cancelled on Thursday because of coronavirus while more teams pulled out of Paris-Nice and Milan-San Remo.
The organisers of the Strade Bianche met with officials in Siena, where the race starts and ends. They concluded that the race could not guarantee meeting the provisions of an Italian government decree issued the day before ordering all major sporting events be held behind closed doors until April 3.
Both the men's and women's races, scheduled for Saturday, were cancelled.
The organisers said on the race web site that they would seek new dates from the international cycling union.
For the time being, there has been no decision on the two other World Tour races scheduled for the coming weeks in Italy, Tirreno-Adriatico (11-17 March) and Milan-San Remo (21 March).
Over the previous 48 hours, several teams had withdrawn from the Strade Bianchi, including Mitchelton, EF, Jumbo, Groupama-FDJ and Ineos.
Other races have been hit by withdrawals.
Astana on Thursday became the third team to pull the plug on Paris-Nice, which starts Sunday, following Mitchelton and Ineos.
The AG2R La Mondiale team said it would be pulling out of all Italian racing up to and including the classic Milan-San Remo.
Astana general manager Alexandr Vinokurov said concern for the health of the team came first.
"We have chosen to protect the health of our riders and staff and to take our responsibility for the society in not further spreading the virus," he said.
Last week, the UAE Tour was cancelled after two Italian staff members on the race tested positive for the COVID-19 virus.
Cyclists, team staff and some media were put under lockdown at hotels in Abu Dhabi where they underwent screening.
On Tuesday the UAE announced six more related cases.
While most teams have been cleared to leave, two French teams, Cofidis and Groupama, have been kept in quarantine in the UAE until 14 March.