It has been officially confirmed that Casey Stoner will miss the next three rounds of the 2009 MotoGP World Championship, ending his title chances.

Ducati's 2007 world champion, who took four podiums (including two wins) from the first five rounds of this season, has been suffering from a mysterious energy-sapping illness in the five rounds since.

Stoner was sick and visibly exhausted after finishing third at Barcelona on June 14 - then struggled with 'severe fatigue' at Assen (third) and Laguna Seca (fourth), prompting extensive medical checks after the US GP.

But those found only 'slight gastritis and mild anaemia', a diagnosis the young Australian was openly doubtful about and he noticed no significant improvement in his physical condition at the following German (fourth) and British events (14th).

Epstein Barr Virus, which can lead to chronic fatigue syndrome, was suggested as one possibility but never proven.

After Donington, Stoner returned to Australia during the summer break to seek consultation from trusted sports doctors.

They are yet to pinpoint the problem, but think a virus during the Catalunya round triggered the fatigue problems. With medical tests continuing, Stoner will withdraw from action until Estoril on October 4 to try and regain full fitness.

“After five extremely difficult races due to my health, I returned to Australia to visit the sports doctors who have looked after me for many years. We have taken the difficult decision not to contest the next three rounds of the championship, to allow my body time to recover from the recent stress,” said Stoner.

“The doctors believe that during the Barcelona race I was suffering from a virus, and, that I subsequently pushed my body too hard, leading to problems that have caused my fatigue since then. The doctors are continuing with many tests to try to understand these problems and make sure it does not happen again.

“I have spoken with Ducati and thank them for their understanding at this time. I feel very sorry for the factory, my team, my sponsors and the fans and I am also disappointed because the bike in the last races has been very competitive. I will be doing everything possible to come back at full strength for Portugal.”

Stoner was leading the world championship at the start of the Catalunya round, but has now dropped to third in the MotoGP World Championship, 37 points behind leader Valentino Rossi.

In the five races since his illness, Stoner has frequently lost pace during the second half of the (dry) races.