American Denny McCarthy has withdrawn from the Travelers Championship before the start of Friday’s second round after testing positive for coronavirus.
England’s Matt Wallace and American Bud Cauley, who played with McCarthy in the first round, tested negative but Cauley has also withdrawn.
Their caddies all tested negative.
American veteran Phil Mickelson set the pace in the second round as his seven-under-par 63 saw him move to 13 under to take the clubhouse lead.
Five-time major winner Mickelson, 50, was a shot in front of American Will Gordon with just a handful of players still on the course.
World number one Rory McIlroy is well in contention in a group of players on nine under after his 68. But England’s Justin Rose is likely to miss the cut after a 73 saw him sit on level par.
McCarthy, 27, is the third player to test positive since the PGA Tour restarted on 11 June.
“I was feeling pretty tired and sore after the round yesterday but didn’t think much of it because I had practiced a lot Monday to Wednesday,” said world number 180 McCarthy, who shot a first round three-under-par 67.
“Last night, I woke up in the middle of the night with additional aches and soreness and sensed something was off.”
Under the PGA Tour’s response plan, 16 tests will be administered for those who had close contact with McCarthy.
McCarthy will self-isolate for 10 days, according to Tour protocols.
Cauley, who tested negative twice on Friday, said he withdrew “out of an abundance of caution for my peers and everyone involved with the tournament.”
Nick Watney withdrew from the RBC Heritage after testing positive last week, while Cameron Champ did so at a pre-tournament screening before the Travelers.
World number four Brooks Koepka and Northern Ireland’s Graeme McDowell also withdrew from the tournament in Cromwell, Connecticut as a precaution after their caddies tested positive.