Rio 2016 Olympics: The Zika Factor—Who's In and Who's Out?

The 2016 Olympic Games was plagued before it had even begun.

An outbreak of the Zika virus, an infection suspected of leading to babies being born with underdeveloped brains, in Brazil this year has put question marks over whether the spectacle should be relocated.

The World Health Organisation (WHO) rejected a call to move or postpone the Games, which has lead to an exodus of athletes from different events.

Here, Newsweek outlines which competitors have withdrawn their participation from Rio 2016 and why.

Tennis

Milos Raonic — The 25-year-old Canadian pulled out three weeks before the Games began. "I am making this decision for a variety of health concerns including the uncertainty around Zika," said the world no. 7.

Simona Halep — The Wimbledon quarter-finalist also cited concerns over the infection for why she was withdrawing.

Nick Kyrgios — Worries about the impact of Zika were not at the forefront of Kygios' withdrawal. The 21-year-old accused the Australian Olympic Committee (AOC) of "unfair and unjust treatment" and "unwarranted attacks" as reasons for his decision.

John Isner — The top-ranked American male on the tour has opted to skip the Olympics, and is set to play at the Atlanta Open instead.

Dominic Thieme — There are "many reasons" why the Austrian decided to drop out of Rio 2016, but Thieme was unwilling to expand on them. He will compete in an ATP event in Mexico, instead.

Roger Federer — A knee injury will see the 17-time Grand Slam champion miss out on the Olympics and the rest of the season. He said he was "extremely disappointed" to not be representing Switzerland at the Games.

Feliciano Lopez — The two-time Olympian cited concerns over the demands of the tennis schedule, with the tournament falling in the lead up to the U.S. Open. The Spaniard described it as a "very difficult decision."

Bernard Tomic — Another player from the tour who cited an "extremely busy playing schedule" as the reason for withdrawing from contention for the Australian tennis team.

Stan Wawrinka — An aggravated back injury saw the Swiss pull out of the tournament just days before the Olympic Games begun.

Golf

Jordan Spieth — Fears concerning the Zika virus in Brazil lead to the world no. 3 dropping out earlier in July. He became the last of the "big four" in golf to withdraw.

Rory McIlroy — The Northern Irishman put his decision to pull out of the Olympics down to concerns over the virus but later said the Games were not the "pinnacle" for golfers. "Most athletes dream of competing in the Olympics," he said. "We dream of winning Claret Jugs and Green Jackets."

Dustin Johnson — World no. 2 Johnson said his plans to have more children in the future meant his concerns about Zika "cannot be ignored." The American described it as "irresponsible" to put his family at risk of contracting the virus.

Jason Day — Ranked as the best golfer in the world, the Australian Day said Zika was not a risk he was willing to take. In a statement, the 28-year-old said: "Competing at the Olympics has always been a major goal, but golf cannot take precedence over my family."

Lee-Anne Price — The South African became the first female golfer to pull out of the Games in June. She said: "I was very much looking forward to the opportunity but I have decided that due to the health concerns surrounding the Zika virus, I will not be participating."

Shane Lowry — It was "with a heavy heart" that Irishman Lowry opted to drop out of the Irish team for the Olympics due to the virus.

Branden Grace — Getting married in November is likely to lead to the South African starting a family and Grace is not willing to risk catching Zika. He hopes to compete at Tokyo 2020.

Marc Leishman — After the Australian's wife almost died in 2015, Leishman consulted doctors and concluded that the trip was too dangerous for his family to make.

Charl Schwartzel — The former Masters champion opted out of representing South Africa at the Games in Rio without specifying a reason.

Vijay Singh — The Fijan, a former world no. 1, expressed his desire to play at the Olympics but cited Zika as his reason for withdrawing in April.

Adam Scott — World no. 7 Scott previously described Olympic golf as an "exhibition" and announced he would not be playing in April. The Australian says his decision is in order to focus on the PGA Tour.

Louis Oosthuizen — Family and schedule were the main reasons the 33-year-old South African put forward as his reasons for withdrawing from the Games.

Graeme McDowell — Set to replace McIlroy for Ireland, the 36-year-old ruled out the possibility of him competing because of fears about the Zika virus.

Cycling

Tejay van Garderen — A pregnant wife lead to the cyclist withdrawing from consideration for the USA team early in June.

Alberto Contador — Four weeks of recovery after the Tour de France saw the Spaniard pull out of contention for Spain's team at the Olympics. He aims to return for the Vuelta a Espana on August 20 as his comeback.

Simon Gerrans — A crash during stage 12 of the Tour de France left the Australian with a broken collarbone. He underwent surgery in Barcelona and has ruled himself out of the Olympic Road Race on August 6.

Basketball

Stephen Curry — A need to rest a sprained knee was the reason put forward by the American as he pulled out of the USA team.

LeBron James — NBA title winner James has decided to opt out of the Games, saying "I could use the rest" after a long season with the Cleveland Cavaliers.