Dubai - World number two Rory McIlroy is exhausted and run down and may have to pull out of next week's inaugural Thailand Golf Championship, his Horizon Sports management team said on Friday.
"Rory has a low white blood cell count and low platelets," a member of Horizon Sports who declined to be identified told Reuters at the Dubai World Championship.
"He has a doctor coming to see him again on Saturday evening and they have just told him to hydrate, take iron and salt tablets and rest.
"We've told the Thailand organisers, they know he's been sick for a few weeks. He wants to play there but I think he'll make a decision tomorrow night," added the source.
"The doctors are saying it's exhaustion, him being run down. The blood count obviously affects his energy levels in a big way."
US Open champion McIlroy, who is locked in a straight fight with Luke Donald to win the money-list at the European Tour's season-ending event in Dubai, has had a gruelling playing schedule in recent weeks.
That, however, did not stop the 22-year-old Northern Irishman finishing his first round in spectacular fashion on Thursday, blitzing his way to five birdies in the last six holes to close within two strokes of leader Peter Hanson of Sweden.
McIlroy needs to win in Dubai and for Donald to finish in a tie for ninth with at least two players to be crowned Europe's number one golfer for 2011.
"The doctors have told Rory not to practice at all and not to go to the gym," the source said on Friday. "He's fine but he just needs to conserve energy.
"It's a virus and he needs time off. They don't know where he picked it up but it's one of those that stays dormant for a couple of weeks and then just kind of flares up."
McIlroy tends to suffer immediately after he finishes a round, the source added.
"He's okay generally as long as he takes the advice of the doctors. He can't avoid being in the sun for six hours a day playing golf, as long as he then stays indoors and keeps his energy levels up.
"Rory said as long as he gets a good night's sleep he feels fine in the morning but then he goes out and plays and within an hour of finishing his blood sugar levels go down and he has to go and rest.
"The other problem is when you are run down like that you're more vulnerable to illness ... so if you go to a tropical climate it could be an issue," added the source.
"We've given the Thailand organisers fair warning because we know its important to them he plays there. He's one of the biggest players in the field next week."
The Bangkok event has a prize fund of $1 million and is the final tournament of the Asian Tour season.