Dustin Johnson has become the most prominent player to test positive for the coronavirus since golf resumed in June, forcing him to withdraw from the CJ Cup at Shadow Creek.
The PGA Tour said in a statement Johnson notified officials he was experiencing COVID-19 symptoms and was given another test that came back positive.
Johnson is the No.1 player in the world and the reigning PGA Tour player of the year after winning the FedEx Cup for the first time.
He has not played since he tied for sixth at the US Open last month.
"Obviously, I am very disappointed," Johnson said in a statement.
"I was really looking forward to competing this week, but will do everything I can to return as quickly as possible.
"I have already had a few calls with the tour's medical team and appreciate all the support and guidance they have given me."
Johnson did not immediately return a phone call seeking comment.
Johnson is the 12th player to test positive since the PGA Tour resumed its schedule on June 8.
It comes one week after world No.16 Tony Finau tested positive with minor symptoms and withdrew from the Shriners Hospitals for Children Open in Las Vegas.
Still to be determined is whether Johnson is able to play the Zozo Championship at Sherwood next week in Thousand Oaks, California.
Under the protocols on the PGA Tour, which are based on guidance from the Centres for Disease Control and Prevention, Johnson is to self-isolate for 10 days dating to when he first experienced symptoms and can return if there are no other symptoms.
That would leave open the possibility of Johnson playing next week at Sherwood, provided he would want to play having gone 10 days without being able to prepare.
Most of the world's best players are in Las Vegas and California for two weeks as part of their preparations for the Masters.
Johnson is scheduled to play the Houston Open on November 5-8 a week before the Masters.
Finau experienced symptoms last weekend, meaning he was eligible to be at Shadow Creek on Wednesday.
Instead, he chose to withdraw.