There is a growing concern surrounding the 2016 Summer Olympics because of the Zika virus outbreak in Brazil. Zika has been declared an international public health emergency by the World Health Organization, and it has some questioning whether they should attend this year’s Games.

The Olympics are set to open Aug. 5 in Rio de Janeiro, and there are no plans to postpone the event. But some athletes have been advised to consider sitting out the Games because of the dangers the virus presents. 

On Friday, International Olympic Committee President Thomas Bach expressed "full confidence" in Brazilian health authorities' efforts to combat Zika, and gave assurances that athletes and spectators should "enjoy safe conditions."

"There is no intention by (any) national Olympic committee to pull out from the Rio Olympic Games. This does not exclude that we are taking this situation very seriously," Bach said.

The virus, which is contracted by mosquito bites, has been linked to microcephaly birth defects in babies, giving pause to some athletes who might consider getting pregnant. A research team recently found Zika in the brains of two babies that lived for less than two days, and nearly 4,000 suspected cases of microcephaly are being investigated. 

Hope Solo has started at soccer goalkeeper for the U.S. in each of the last two Olympics, but she could stay home this summer because of Zika.

“If I had to make the choice today, I wouldn’t go,” Solo told Sports Illustrated recently. “I would never take the risk of having an unhealthy child.”

Aside from pregnancy risks, Zika isn’t considered a particularly grave threat. Eighty percent of people infected won’t have symptoms, and most of those affected exhibit only mild symptoms, including fever, rash, joint pain and red eyes. 

It’s not unusual to have an outbreak of some sort at major sporting events like the Olympics or the World Cup. According to CNN, 82 cases of measles occurred at the 2010 Winter Olympics, while 65 people contracted Norovirus at the 2006 World Cup in Germany.

Zika certainly isn’t the only heath risk facing those who visit Rio for the Olympics. Parasites found in the soil are a potential threat, as are other diseases spread by mosquitoes.

In order to lower the risk of infection, Brazilian authorities say they will begin inspections of Olympic facilities four months before the Games are set to start, in order to eliminate mosquito breeding grounds. There will also be daily sweeps once the Olympics have begun.