American cyclist Tejay van Garderen has ruled himself out of the Olympic Games due to fears he may contract the Zika virus and pass it to his pregnant wife.
Zika, which is carried by mosquitoes and has been linked to serious birth defects, is affecting large parts of Latin America and is prevalent in both Brazil and Rio de Janeiro.
The World Health Organisation has declared it a global emergency and a group of 150 health experts last month demanded the Olympics be relocated or postponed.
Van Garderen was a strong contender to lead the United States' team in the men's road race and would also have been a candidate for one of their two places in the time trial, but he doesn't want to risk being infected.
He told cyclingnews.com: "I know the risks are small, and there are precautions you can take, but the fact is I just don't want to risk bringing anything into the house that could potentially have an effect, however small the chances are."
Zika has been blamed for cases of microcephaly - when babies are born with abnormally small heads - and clinical studies have also shown health implications for adults, including the debilitating and sometimes fatal Guillain-Barré syndrome.
Carlos Nuzman, the head of the Rio organising committee, told a meeting of the International Olympic Committee on Thursday that cases of Zika will significantly drop from June to September and claimed that Zika poses "no public health risk" that would warrant calling off the Games.