Branden Grace has been ruled out of next week's US PGA Championship after testing positive for coronavirus during the Barracuda Championship.
The 32-year-old South African was in a share of second at the PGA Tour event in Nevada but withdrew before the third round and will now go into isolation for 10 days.
Brace said he felt tired Friday night and thought it had to do with playing in altitude.
He was tested to be sure, and it came back positive for COVID-19 and he withdrew.
"I felt great all week," Grace said.
"Last night, I was tired and thought it had to do with the altitude.
"This morning, I notified the PGA Tour about my symptoms before going to the golf course.
"I wanted to get tested out of respect for my peers and everyone involved with the tournament.
"While it is unfortunate given my position on the leaderboard, the most important thing is our health."
Under PGA Tour guidelines, Grace has to self-isolate for 10 days and be without a fever for 24 hours before returning.
The rescheduled PGA Championship, which will be the first major of 2020, starts at TPC Harding Park in San Fransisco on Thursday.
A PGA Tour statement said: "The PGA TOUR has implemented its response plan in consultation with medical experts, including working with those who may have had close contact with Grace."
Grace's caddie tested negative for COVID-19 but will quarantine for a period of 14 days.
The PGA Tour said its contact tracing did not lead to additional testing.
Grace has played in every major dating to the 2014 British Open and holds the major championship record with a 62 at Royal Birkdale in the 2017 British Open.