Updated at 3 p.m. ET: Brooks Koepka has officially withdrawn from the Travelers Championship, joining what is now a list of five players who have pulled out for reasons related to COVID-19.

The world No. 4 withdrew after a positive test by his caddie, Ricky Elliott, and though reports indicated that Elliott's second test was negative, Koepka maintained his decision to WD. He is joined on the withdrawal list by brother Chase Koepka, Webb Simpson, Graeme McDowell and Cameron Champ. Of that group, only Champ is known to have failed a test.

"I haven’t tested positive for COVID-19, but as I’ve said all along, I’m taking this very seriously," Koepka said in a statement. "I don’t want to do anything that might jeopardize the health of any player in the field or his ability to compete. The right thing to do right now is get home, support Ricky and feel confident that I’m doing what I can do protecting my fellow Tour members, my PGA Tour friends and everyone associated with the Travelers Championship this week."

Koepka said he plans to skip the next two events, as well, before hopefully returning at Memorial.

Original story: Brooks Koepka reportedly plans to withdraw from the Travelers Championship after his caddie, Ricky Elliott, tested positive for COVID-19.

According to a Golfweek report, Koepka, Elliott and swing coach Claude Harmon III all took additional tests Wednesday after playing a Tuesday practice round with Graeme McDowell. McDowell planned to withdraw Tuesday following a positive test result for his caddie, Ken Comboy, who had not traveled to Connecticut for the event.

Koepka, Harmon and McDowell all reportedly came back negative with their secondary tests, but Elliott – who had already tested negative for the virus upon arrival Monday – turned up positive.

"I'm going to pull out to protect everybody else. I think it's the right thing to do," Koepka said. "I don't want to risk anyone's life if they have respiratory issues or underlying conditions. The only way this Tour can continue is if guys do this sort of thing and be proactive about it."

Koepka's would be the third coronavirus-related withdrawal from this week's event, as Cameron Champ also withdrew Tuesday after testing positive. Last week Nick Watney became the first known PGA Tour player to contract the virus and withdrew ahead of the second round of the RBC Heritage.

Ranked No. 4 in the world, Koepka was coming off a seventh-place finish at Harbour Town that marked his first top-10 result since last year's Tour Championship. He had played each of the first two events since the Tour's return from hiatus, finishing T-32 at Colonial earlier this month, and was on-site early in the week to watch his brother, Chase, Monday qualify for this week's 156-man event at TPC River Highlands.

Koepka reported that both he and Elliott were asymptomatic, and said that his caddie has his "full support" as he enters a period of self-isolation. Koepka will reportedly make his decision about returning home to Florida or potentially quarantining in Connecticut based on pending test results for his girlfriend, Jena Sims, and the personal chef who had been preparing food for them in their rental home.

"I'd rather be safe than sorry," Koepka said.