File photo shows 2016 Rio Olympics Chief Medical Officer Joao Grangeiro attends a briefing on Zika virus for international media in Rio de Janeiro, Brazil, June 7, 2016. [Photo/Agencies]

Ireland's Shane Lowry, the world number 25 who finished joint runner-up in this month's US Open, also withdrew on Tuesday and said his decision was based on firm medical advice.

"While I am bitterly disappointed to be missing out on that experience and the opportunity to win an Olympic medal for Ireland, on this occasion I have to put my family's welfare first," said Lowry who recently married.

Ireland Olympic golf team captain Paul McGinley said the withdrawals were not good for the image of the sport.

"I agree it doesn't particularly reflect well on golfers when they seem to be the only ones withdrawing but when it is for their own personal reasons, we have to respect that," he told national Irish broadcaster RTE.

"The risk is very, very, very small but ultimately it's a risk they're not willing to take."

The Rio Olympics, the first in South America, take place from Aug 5-21.