"They are concerned and are being given advice on how to proceed," Cassius Duran, a former Brazilian diver, told reporters at the inauguration of the remodeled Maria Lenk Aquatic Center, where the Olympic diving will be held in August.
Duran said organizers were telling athletes to use repellents to protect themselves against mosquito bites, the primary means of transmission of the virus.
The test event, which runs from Feb. 19 to 24, is a stage of the Diving World Cup and 270 athletes from 50 countries are due to compete.
Athletes and visitors planning to come to the Olympics have expressed concern about Zika, a virus linked to birth defects in newborns, which has been reported in more than 30 countries, according to the World Health Organization.
U.S. tennis player John Isner said on Friday that he was taking precautions before the Rio Open scheduled to begin on Monday, but said he was not very worried and had no intention of skipping the Olympics because of Zika.
"This will not be a reason to not go to the Games," said Isner, ranked No. 12 in the world and No. 1 in the United States. "In six months, I think they will have this well under control."
Brazil late on Friday said it was investigating the potential link between Zika infections and 4,314 suspected cases of microcephaly, a condition marked by abnormally small head size that can result in developmental problems.
Of those cases, 462 were confirmed as microcephaly and 41 were determined to be linked to the Zika virus.
On Friday, British researchers reported that Zika virus can be detected in semen for 62 days after a person is infected, adding to evidence of the virus’s presence in fetal brain tissue, placenta and amniotic fluid.
Olympic organizers previously said the games would be held during Rio's winter when there tends to be fewer mosquitoes. However, a Reuters report this week showed there was not always a decline in mosquito-borne infections during that season.
Rio's Mayor Eduardo Paes said the city was pulling out all stops to ensure the safety of athletes.
"We are doing everything to avoid any type of danger for any of the athletes who come," he said.
"There is a Zika problem, but I think there is also a certain amount of exaggeration and ignorance. It is this that frightens more than the virus itself," he said.
(Adds details on suspected cases of microcephaly, information from British researchers and comment by U.S. tennis player John Isner, paragraphs 6-10.)
(Reporting by Pedro Fonseca; Writing by Stephen Eisenhammer; Editing by Toni Reinhold)