England's Matt Wallace and Bud Cauley of the United States, who played with McCarthy in the first round, both tested negative.

Cauley also decided to withdraw, while Wallace missed the cut for the second round.

All of their caddies also tested negative.

Both McCarthy and Cauley sat at par on the leaderboard when they decided to withdraw, with the former being the third professional to return a positive test since the PGA Tour resumed on June 11.

"I was pretty tired and sore after the round yesterday but didn't think much of it because I had practised a lot Monday (June 22) to Wednesday (June 24),

"Last night, I woke up in the middle of the night with additional aches and soreness and sensed something was off."

He will now self-isolate for 10 days in accordance with Tour protocols.

PGA Tour Commissioner Jay Monahan added: "Denny has our full support as he self-isolates here in Hartford and recovers, and I know I speak for the entire Tour membership in thanking him for doing the right thing in requesting an additional test before heading to the golf course today."

It follows the news of five players on the Tour withdrawing from the Championship after American player Cameron Champ became the second to test positive for COVID-19.

Those included some of the sport's biggest names, such as Brooks and Chase Koepka, Webb Simpson and Northern Ireland's Graeme McDowell.

McDowell and Brooks Koepka decided to withdraw after their caddies tested positive.

Nick Watney was the first to test positive and was forced to withdraw from the RBC Heritage tournament last week.

In the Travelers Championship, American Phil Mickelson sits top after two rounds at 13 under par, a shot ahead of compatriot Will Gordon and Canada's Mackenzie Hughes.

World number one Rory McIlroy is four shots off the lead, with other noticeable players, including Americans Bryson DeChambeau and Dustin Johnson on eight and seven under par, respectively, and Spain's Jon Rahm on six under.