Moto2 championship contender Jorge Martin will miss this weekend's race at Misano having tested positive for COVID-19.
A mechanic from another team has also tested positive, but both are said to be asymptomatic.
Neither have travelled to the event and are instead in isolation at their respective bases.
“Jorge Martin has been unable to travel to Misano due to a positive test for COVID-19,” read a statement from the Red Bull KTM Ajo team.
“The Spaniard feels well and is quarantined at home, respecting the safety protocols of the health authorities.
“Red Bull KTM Ajo Moto2 team hope that he will be able to make a speedy return to the paddock to continue the great work done at recent rounds.”
Team Manager Aki Ajo is optimistic that the Spaniard will be able to return for the second round at Misano which takes place on the following weekend (September 18-20).
Martin is currently tied for second in the championship, although technically third on a countback, at eight points behind Luca Marini.
The 22-year-old and the unidentified mechanic make for three people normally in the paddock who have tested positive for the coronavirus now after a television crew member became the first, last month in the Czech Republic.
Australian Remy Gardner (SAG Racing Team) is currently ninth in the championship, 46 points off the lead.
Practice for the San Marino round starts this evening (AEST).