The season-opening Qatar MotoGP, scheduled to take place on March 8, was cancelled Sunday because of the spread of the coronavirus, the international motorcycling federation (FIM) announced.
"Due to Qatar travel restrictions brought into force affecting passengers from Italy (amongst other countries), the premier class will not race at the Losail circuit," the FIM said.
However, the Moto2 and Moto3 world championship races will go ahead as planned at the desert track as riders and teams were already in the Gulf state preparing for the event with winter testing.
As the coronavirus has spread, Italy has become the hardest-hit European country with 34 deaths and over 1,600 people infected.
"As of today, all passengers arriving at Doha on direct flights from Italy, or having been in Italy in the past two weeks, will be taken straight to quarantine for a minimum of 14 days," added the FIM.
"Italy clearly plays a vital role in the championship and in the MotoGP class - both on track and off - and therefore the decision has been taken to cancel premier class competition."
Six riders in the elite class are Italian - seven-time MotoGP world champion Valentino Rossi, 2019 runner-up Andrea Dovizioso, Danilo Petrucci, Francesco Bagnaia, Franco Morbidelli and Andrea Iannone.
Ducati and Aprilia are leading Italian manufacturers.
MotoGP riders and teams were in Qatar from February 22-24 for the final session of winter testing.
- 'Delicate and strange time' -
"Obviously it's a big shame to have to cancel this first race of the season, as we were all really ready to start, and so were the fans," said Suzuki team boss and Italian native Davide Brivio.
"Some of our team staff stayed in Qatar following the test days, as we were aware of the seriousness of the outbreak. But at this time the most important thing is the safety of the people, and we have to respect the decision made by the local authorities and by the MotoGP officials.
"It's a delicate and strange time for everyone around the world and we need to take things race-by-race and see what develops in the coming weeks."
French rider Fabio Quartararo, who will replace Rossi at the Yamaha factory team in 2021, said he had been ready to get the season under way.
"I was waiting for the first race since the end of last year," the 20-year-old tweeted.
"I am sad and disappointed after all our work but it is what it is. We'll see now when the first race will be."
Qatar was to be the first of a 20-race MotoGP season and it becomes the latest motorsports event cancelled because of the spread of coronavirus.
The Chinese Formula One Grand Prix, which was set for April 19 in Shanghai, has already been axed as has the March 21 Formula E race slated for Sanya on the Chinese island of Hainan.
However, the inaugural F1 race in Vietnam, on April 5, is still going ahead.
With the Qatar round cancelled, the Thailand MotoGP at Buriram on March 22 now becomes the season-opener.
It was announced last week that visitors to the circuit will face rigorous health screening and be given hand sanitiser and facemasks to keep the event coronavirus-free.
Thermal screening will be used at the racetrack's entrances, hotels will look out for anyone showing symptoms, and a 'Buriram Healthy' app will provide up-to-date health information.
Ducati's Italian rider Andrea Dovizioso celebrates winning the 2019 Qatar MotoGP