The world No.3, who will be competing for gold as golf returns to the Games after a 112-year absence, had cast doubt on his participation earlier this month after revealing he and his fiancee, Erica Stoll, may consider starting a family in the near future.
The World Health Organization (WHO) declared Zika, a mosquito-borne virus, a global public health emergency four months ago.
It has been shown to cause microcephaly in babies and is linked to some cases of muscle-weakening disease Guillain-Barré syndrome in adults.
The U.S. Centers for Disease Control and Prevention has told pregnant women to stay away
from areas where Zika is prevalent and has issued guidelines for those who may wish to become pregnant.
"I've sought out some advice and I had two dead shoulders for about four days last week because I got my shots and whatever I needed to get for going down there," McIlroy told a press conference on Wednesday.
"Obviously, there's no vaccination for Zika. I think what the health experts are really worried about, it's not the individual cases.
"It's the fact that 500,000 people go to Rio and they spend three weeks at the Games, they go back out of Rio and some might have contracted Zika and don't know about it, and then all of a sudden instead of it being this virus that's contained in a certain part of the world, it's now a global epidemic.
"And I think that's the real concern. So for me to go down there, even if I was to get Zika, it's six months and it's a virus and it works its way out of your system.
"And it's nice that we can come back, and [if you] feel like you've had some of the symptoms down there, you can get tested for it, and it's either a yes or a no you've had it."
McIlroy is not the first golfer to speak publicly of his concerns over Zika. Fiji's Vijay Singh and Australia's Marc Leishman have already pulled out of the Games because of the virus.
But McIlroy, who will compete for Ireland in Rio, says he feels confident in the medical advice he has been offered and is "ready to play."
"I feel like the advice I've sought out over the past 10 days has put my mind at ease and makes me more comfortable going down there knowing that, even if I do contract Zika, it's not the end of the world," he said.
"It takes six months to pass through your system and you're fine."