Nick Watney received a positive test before his second round at Hilton Head, while Cameron Champ tested positive before the Travelers Championship and Denny McCarthy after his first round at the TPC River Highlands.
Dustin Johnson gained the Travelers Championship on Sunday to conclude a extended drought and prolong his vocation-extended period victory streak to 13.
Johnson closed with a 3-under 67 for a one-stroke victory over Kevin Streelman at fan-free TPC River Highlands.
The former world No. 1 claimed his 21st PGA title to mark his 13th consecutive season with at least one victory, a feat matched only by an elite group of players that includes Jack Nicklaus, Arnold Palmer, Lee Trevino and Tiger Woods.
Mackenzie Hughes, who shot a first-round 60, had a 67 to tie for third with 23-year-old Will Gordon at 17 under.
But the 2014 champion was unable to bogey the last as he settled for a 67 and the clubhouse lead on 18 under, leaving Johnson needing just a par to win for the first time since the WGC-Mexico Championship in February previous year.
"I'm definitely proud of myself for continuing the streak.it was a long time between wins though - hopefully it won't be that long for the next one", Johnson said in a televised interview.
He was two strokes behind Johnson on the 17th fairway when the weather horn blew for an hour-long storm delay.
His ball buried deep in the bank of a bunker, Todd shanked his pitch and then came up short with an ambitious flop-shot before a putt up the slope also lacked the pace to reach the putting surface. After securing his par, a rain delay halted proceedings and on returning to the course, Johnson immediately bogeyed the 16th hole to heap the pressure on himself.
It was sort of quite consistent and sort of building sort of rounds very nicely, a lot of pars, a few birdies, not many mistakes.
Gordon, who had no status on either the PGA Tour or the Korn Ferry Tour, had seven birdies in a 64.
After a bogey on the seventh saw him relinquish a share of the lead, Johnson bounced back with a curling 27-foot birdie putt on the eighth to get back to 18 under. He earned a special temporary card and unlimited exemptions for the rest of the season.
American Brendon Todd, who had been in the lead after a career-low 61 in the third round, self-destructed on No. 12 with a triple bogey and failed to recover, ending the tournament tied for 11th on 265 after a five-over 75.
World number one Rory McIlroy climbed into a tie for 11th thanks to a three-under 67.
The PGA Tour is making some tweaks to its coronavirus policies as a result of this week's issues.