Rory McIlroy watches his shot on the 12th hole during the first round of the Travelers Championship at TPC River Highlands on Thursday in Cromwell, Conn. Seth Wenig/Associated Press

CROMWELL, Conn. — Rory McIlroy fought off a sinus bug to shoot an 8-under 62 on Thursday for a share of the first-round lead with J.T. Poston in the Travelers Championship.

Coming off a fifth-place tie Sunday in the U.S. Open after winning the Canadian Open the previous week, the second-ranked McIlroy had a bogey-free morning round – highlighted by a 47-foot birdie putt on the par-4 seventh. McIlroy matched the lowest opening round of his PGA Tour career. He finished with a tap-in birdie on the ninth hole after a 332-yard drive and 44-foot chip just past the pin.

“It’s like U.S. Open rehab coming here,” the four-time major champion said. “I like coming here the week after the U.S. Open, it sort of gives you an opportunity to shoot low scores and get after it.”

Poston had five straight birdies on Nos. 13-17 and made the turn at 6-under 29, giving rise to thoughts of Jim Furyk’s record 58 on the same TPC River Highlands course in 2016. Poston parred the first six holes on front nine and birdied Nos. 7 and 9 to cap a bogey-free round.

“I gave myself a few looks, but kind of made a bunch of pars to start the front, so that was kind of out of the picture after a little while,” said Poston, the 2019 Wyndham Championship winner. “I might have thought about it a little more if I had made a couple of early birdies.”

Xander Schauffele and Martin Laird were a stroke back. Patrick Cantlay, Charles Howell III and Webb Simpson, who played alongside McIlroy, were two shots back at 64.

“We kind of fed off each other,” Simpson said about McIlroy. “The holes started looking bigger and bigger. A lot of putts were made.”

LPGA: In Gee Chun breezed to an 8-under 64 to take a five-stroke advantage after the first round of the Women’s PGA Championship in Bethesda, Maryland, and no player has ever been further ahead after 18 holes at a women’s major.

While most of the field slogged through the day on the wet Blue Course, Chun birdied seven of eight holes during one stretch. She was seven shots ahead when she finished her round and ended up tying a record for the largest 18-hole lead at a major. Mickey Wright led this tournament by five after the first round in 1961.

“I don’t know what golf course In Gee is playing,” defending champion Nelly Korda said after finishing her round of 71.

Pornanong Phatlum and Hye-Jin Choi shot bogey-free rounds of 69 to cut Chun’s lead to five, but that was still a big enough advantage to tie Wright’s mark. The 1961 tournament was one of a record four victories by Wright at this event. Chun is trying for her first.

CHAMPIONS: Jay Haas has been shooting his age or better for the last three years, just never on a stage quite like the U.S. Senior Open in Bethlehem, Pennsylvania.

Haas steadied himself from an up-and-down start at soggy Saucon Valley and played much younger than his 68 years down the stretch, posting a 4-under 67 to share the lead with Mark Hensby after the opening round.

Haas became the fifth player in U.S. Senior Open history to shoot his age, joining Tom Watson, Hale Irwin, Harold McSpaden and Jerry Barber, who did it nine times. Barber was the oldest first-time winner of a major in the 1961 PGA Championship.

EUROPEAN TOUR: Li Haotong shot 10-under 62 to lead after the first round of the BMW International Open as the European tour continued to allow players from the breakaway Saudi-backed LIV series to compete.

Li tied the course record, finishing the round with his second eagle of the day on the par-5 ninth hole after a big approach shot left him a 4-foot putt. He leads by one stroke over Daan Huizing and two over third-place Nicolai von Dellingshausen.

Former major winners Sergio Garcia, Louis Oosthuizen and Martin Kaymer were among the players signed to LIV to tee off Thursday in the first European tour event to start since the PGA Tour said June 9 it would suspend any of its players who join LIV. Kaymer was the best of the LIV players Thursday, finishing as one of six players tied for fourth on 6 under, four strokes behind Li. Oosthuizen was on 2 under and Garcia 1 over.