By Mark Lamport-Stokes

OAKMONT, Pennsylvania (Reuters) - Concerns over the Zika virus at the 2016 Rio Games have been a hot topic of conversation among the golfers at this week's U.S. Open, with many of them opting to play a waiting game until August.

Earlier this month, world number one Jason Day expressed doubts for the first time over whether he would compete at the Summer Olympics in Brazil while third-ranked Rory McIlroy on Tuesday said his focus, for the moment, was on golf's majors.

"It's still a good bit away," Northern Irishman McIlroy told reporters at Oakmont Country Club about the Aug. 5-21 Rio Olympics. "We've got three (golf) majors to play. Everyone's really concentrating on them coming up. That's our big focus.

"Looking beyond that, Rio is part of our schedule now and something we should get excited about. Golf in the Olympics, it's great for the game. It should hopefully grow the game in different parts of the world that haven't been exposed to golf.

"The chatter has been somewhat quiet so far, mostly everyone's just been talking about Zika. But once we get these majors out of the way ... our attention will turn to that, and I think everyone will start to get a bit more excited about it."

After this week's U.S. Open, the British Open will be played at Royal Troon in Scotland from July 14-17 before the season's final major, the PGA Championship, is staged at Baltusrol in New Jersey from July 28-31.

Masters champion Danny Willett, speaking before he set off for a practice round at Oakmont Country Club on Tuesday, said he was excited about the Olympic Games but would opt not to go if his family's health was at risk.

"It's still up in the air," said Willett, whose wife Nicole gave birth to their first child, Zachariah, on March 30. "Little man's just under 12 weeks old, and if me and Nic were ever thinking about having more kids, we wouldn't leave it too long.

"There's obviously a little bit of a worry right now with everything that's going on (with Zika). You've seen from a few guys that have pulled out. We're down to play at the moment," said Englishman Willett.

"In August, when the Olympics is, it's obviously wintertime down in Brazil so the threat becomes a little bit less in itself. But I'd never put my family or myself in any threats to go play a golf tournament, regardless of what it is."

U.S. health officials have concluded that infections by the mosquito-borne Zika virus in pregnant women can cause microcephaly, a birth defect marked by small head size that can lead to severe developmental problems in babies.

TEMPORARY PARALYSIS

The World Health Organization has said there is strong scientific consensus that Zika can also cause Guillain-Barre, a rare neurological syndrome that causes temporary paralysis in adults.

The connection between Zika and microcephaly first came to light last fall in Brazil, which has now confirmed more than 1,400 cases of microcephaly that it considers to be related to Zika infections in the mothers.

Australian Day had previously been vocal in his support for golf's return to the Olympics after an absence of more than a century but he and his wife, Ellie, want to make "an educated decision" as they consider having a third child.

"There's a lot of guys who are on the fence about it because they don't want to put themselves in harm's way," said Day.

"We're just really trying to monitor what's going on and make an educated decision because obviously we're not done having kids."

Fellow Australian Adam Scott previously announced he would also skip the Rio Games, though not because of Zika concerns but more due to his belief that golf does not belong in the Olympics.

Fiji's Vijay Singh, and fellow major winners Louis Oosthuizen and Charl Schwartzel of South Africa, will also be among the absentees for the Aug. 11-14 men's golf competition.

(Editing by Frank Pingue)