One of Annalise Murphy's rivals to make the podium in the Women's Laser Radial class has fallen ill, with the polluted Rio waters said to be the likely cause of a gastro-intestinal infection.
Four years on from winning bronze in London, 30-year-old Evi van Acker was considered among the favourites to top the podium in Brazil.
However, she has become the first sailor to become sick racing on the waters that have been under so much scrutiny leading into the Games.
The Belgian sits 10th overall after six Laser Radial races but the Belgium Olympic and Interfederal Committee (BOIC) says recovery from a "severe gastro-intestinal infection" has hampered her performance.
Van Acker's coach Wil van Bladel believes she contracted the infection training in Rio last month, saying: "The likelihood she caught it here during contact with the water is very big."
World Sailing spokesperson Darryl Seibel believes it is an isolated incident among the athletes, underlining the body's dedication to making the conditions safe for racing.
"She's the only one of the 380 athletes who are here competing who has indicated they're not feeling well," he told Press Association Sport.
"We have a team of medical and technical experts and they review the latest testing data that we get from the government each morning.
Seasick @Annalise_Murphy enjoying Rio experience https://t.co/0xtivQjV4X
— RTÉ Sport (@RTEsport) August 10, 2016
"The standard they're using is the World Health Organisation standard for primary contact and so far we've been able to meet a field of play that meets that standard every day during the Games and the lead up to the Games.
"But it's something we of course take very seriously and that's why our medical and technical team look at that every morning.
Murphy sits in second place overall after excelling in heavy-weather conditions when the action resumed in Guanabara Bay on Wednesday.
The Rathfarnham woman has been battling an affliction of her own - sea sickness.
"I get seasick, so I had to put seasickness bands on my wrists to stop me getting sick!” she revealed. Murphy is back in action on Friday at 5.05pm irish time.
