Rossi writes on twitter how he woke up yesterday morning with "leg pain and mild fever" and immediately called his doctor for testing.
The first "quick test" was negative, but late yesterday afternoon the nine-time world champion was informed that he had been affected by the virus.
The World Cup circus is in an intense competition period.
This weekend, a competition was run at Le Mans.
Now two competition weekends await in Spain.
Both competitions are decided in Aragon.
Followed the protocol
The 41-year-old says that he followed the "protocol" closely and isolated himself after Le Mans.
After a negative test on Tuesday, a gloomy message came to the Italian icon.
- I can only follow the doctor's advice and hope that I will soon feel better.
We recently told you that Rossi has signed for Petronas Yamaha SRT for next season.
Swedish Johan Stigefelt is the operational manager in the stable and handled the contract negotiations with the icon.