Becoming an Olympian requires devoting yourself to a single cause at the exclusion of virtually everything else. Years of training, often in solitude, with little financial security, all in the hope of a payoff that comes just once every four years. Miss your chance, and suffer even more lonely years trying to claw your way back. For those gifted and lucky enough to make it to the Games, the last thing they want is to worry about life outside of competition. This year, however, that may be impossible as the 2016 Summer Olympics take place in the nation at the center of the Zika epidemic.

No American athletes have pulled out of the Games because of concerns over the mosquito-borne disease. But the threat of Zika has thrown an unexpected and unwelcome wrinkle in the plans of American athletes as they prepare for the most important moments of their lives this summer in Rio. The questions are particularly acute for those planning to have children now that U.S. health officials confirmed that Zika causes microcephaly and other severe brain abnormalities and can be spread through sexual contact. The Brazilian government has confirmed 1,168 cases of microcephaly linked to Zika in the country. The World Health Organization estimates that more than 3 million people could be infected with Zika in the Americas this year.

“It should be a concern for all the athletes competing,” says Hope Solo, the star goalkeeper for the U.S. women’s soccer team. In early February, Solo told SI.com that concerns over Zika would keep her from the Olympics if she had to decide at that moment. She now says she plans to go but acknowledges that worry about the disease will linger.

“It sucks, it does,” says Dawn Harper-Nelson, who won the gold medal in the 110-m hurdles in Beijing in 2008 and a silver in London in 2012. “It sucks that it’s on the news, that that’s what we’re talking about. But if I think about that today, it affects me being on the podium in August.”

Maria Michta-Coffey, an American racewalker with a Ph.D. in biomedical sciences from the Icahn School of Medicine at Mount Sinai in New York City, says she planned to start a family immediately after the Olympics in August. “The idea was to take a vacation and conceive as soon as the Games are over, maybe in Brazil itself,” she says. Now those plans are on hold. And an abundance of caution may keep her husband and longtime training aide from coming to Brazil with her.

“I like to think of ourselves as a team allowing her to make it to that level,” says Joe Coffey, a high school physics teacher. “I have a sweatshirt that says ‘Water Boy’ on it. I’m her aide at all her various competitions. It’s a lot of time and effort and conceding on my part, in terms of missing birthdays and family functions, waking up early for workouts, and things of that sort. So you want to see the fruits of your labor. Especially since these Olympics are going to be the last time most likely that Maria’s competing at a super high level. The idea of not going to the Olympics to see your wife compete is a scary thought in itself.”

MORE: The War Against Mosquitoes: A Tale From the Front Lines

Archer Brady Ellison, who won a silver medal in 2012 in London, wants to start a family in the near future. Because of Zika, his fiancée has decided to skip the trip to Rio. “If you can prevent something, even if it’s a small chance of happening, why not do it?” says Ellison.

The Centers for Disease Control and Prevention advises pregnant women not to travel to areas where Zika is spreading because a mosquito bite could put the fetus at risk of developing microcephaly. Dr. Amesh Adalja, an infectious-disease specialist at the University of Pittsburgh Medical Center’s Center for Health Security, says current guidelines recommend that a woman returning from a Zika-prone region wait about eight weeks before trying to conceive, in case she has an asymptomatic infection. Men, says Adalja, “need to practice safe sex for at least two to six months after coming back, based on what we know today. The sexual-transmission question has made it much more complicated because you’re now viewing men as vectors of spread to pregnant women anywhere.”

The Olympics will take place in winter in Brazil, when the risk of infection is expected to be lower than it is today. “It’s a time of the year for low transmission of mosquito-borne diseases in Rio de Janeiro,” says Dr. Maurício Lacerda Nogueira, an infectious-disease researcher based in the Brazilian city of São José do Rio Preto. “Because it’s colder, and it’s dry season.” Nogueira thinks a bigger risk for those attending and competing in the Games is dengue, a mosquito-borne disease that can carry more series symptoms, like intense stomach pain, disorientation, heavy bleeding and even death. Yet he says the likelihood of catching dengue while at the Games is also very low.

Still, Rio’s organizing committee is recommending that athletes and spectators do whatever they can to avoid mosquito bites during the Olympics. Wear long-sleeved pants and shirts while outside, stay in air-conditioned rooms and use insect repellent. “In the case of Zika, we need to inspect the venues every single day, especially for stagnant water,” says Mario Andrada, chief spokesperson for the Rio 2016 committee. “Most of these venues have just been construction sites, and we all know that construction sites carry spaces that are favorable for mosquitoes.”

MORE: See Inside a Rehab Center for Babies With Likely Zika-Related Birth Defects

Many other Olympians, however, are unfazed. “It’s not like if you go to Rio, you’re flipping a coin,” says three-time Olympic gold medalist Kerri Walsh Jennings, speaking from a beach-volleyball test event in Rio in March. Walsh Jennings competed in London while she was pregnant. “I don’t think it’s as dramatic as being presented.” These athletes insist they trust the U.S. Olympic Committee, which has named three infectious-disease specialists to an independent advisory group that will draw up Zika recommendations and guidelines for the Olympians, to look after their health. “It’s going to be up to each individual athlete to make his or her decision whether or not they want to attend,” Scott Blackmun, CEO of the USOC, said in March. “I’m not aware of a single athlete who has made a decision not to attend because of any conditions in Rio.” (On April 12, golfer Vijay Singh, of Fiji, cited both Zika and his desire to focus on the PGA tour as reasons for skipping the Games.)

Wrestler Jordan Burroughs won gold in London and is hoping to defend his medal in Rio. His wife is due to give birth to the couple’s second child in mid-June, before the start of the Olympics, but he says that won’t keep the whole brood from coming to Rio. “I’ve been bitten by a lot of mosquitoes in my life,” says Burroughs. “But I haven’t won a lot of gold medals. So the decision has already been made. The sacrifice is in order. We’re going. And we’re bringing the family.”

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Write to Sean Gregory at sean.gregory@time.com.