With the 2016 Summer Olympics fast approaching, many are preparing for one of the world’s largest events. However, this year’s much anticipated Olympics might be plagued by mosquitoes carrying the Zika virus.

The Zika virus is carried and spread by mosquitoes, causing symptoms such as a fever, rash, joint pain, and or irritated eyes. Because of these rather mild symptoms, people don’t realize they may be infected. However, if the Zika virus is contracted while pregnant, it can cause serious birth defects for the child such as microcephaly.

Rio de Janeiro, Brazil, host city for this summer’s Olympics, is a country where Zika has broken out. Many participating countries as well as individual athletes are considering not attending this summer’s games.

Spanish basketball player Pau Gasol has made it public that he might not be attending this summer’s Olympics due to the Zika outbreak. Gasol is not alone, British tennis player Andy Murray also is considering this option.

For other athletes the Zika virus does not worry them. Irish golfer, Rory McIlroy stated in an interview with Golf.com that his mind is at ease and now knows that contracting the virus does not mean it’s the end of the world. Jamaican sprinter Usain Bolt said on NBC’s Today Show that he is not worried about the mosquitoes because “they can’t catch him.”

Some countries have tried to find solutions to keep their athletes safe if they attend the games. South Korea has been designing “mosquito proof” uniforms for their athletes to wear. The uniforms were specially made to repel mosquitos by infusing mosquito repellents and other chemicals into the team’s uniforms.

The athletes and their countries are not the only people concerned. There is a group of over 200 doctors, bioethicists, and public health specialists who believe that no one should attend this summer’s Olympics unless it is moved from Brazil. This group posted an open letter online exclaiming that the Olympics should be postponed “in the name of public health.”

Major League Baseball (MLB) has already moved games from Puerto Rico to Miami because of Zika worries. Detroit Tigers pitcher Francisco Rodriguez stated in an interview with ESPN that he contracted the virus, and is now urging Olympic athletes to “do their homework” before they choose whether or not to attend. Rodriguez is warning other athletes about the virus after he has spent two weeks in the hospital dealing with headaches, body aches, and joint pain.

However, the World Health Organization (WHO) claims that moving the Olympics from Rio de Janeiro will not change the international spread of the Zika virus. WHO has advised for pregnant women not to travel to the Olympics, and for everyone to follow public health travel advice.