The world-class athletes that will descend on Rio de Janeiro for the Summer Olympics in August understandably make a point of keeping themselves healthy. After all, more than Olympic glory is riding on their fitness.

For some, professional careers await after the Games. All of them, though, have spent a lifetime dedicated to fitness and nutrition, ensuring they take care of their bodies. They spend hours each week exercising and training, and they're devoted to eating and sleeping well.

But in Brazil looms the prospect of an opponent they can't defeat through all of the methods they've learned through their training: the Zika virus. The virus, which is carried by mosquitoes and transferred to humans through bites, has hit Brazil particularly hard since its outbreak there in 2015.

Zika has been discovered in at least 33 countries but is concentrated in Central and South America, according to the Centers for Disease Control and Prevention. In Brazil, 1.5 million people are believed to have been infected.

The CDC has indicated that the virus also can be spread through sexual contact. According to some, there's plenty of that in the Olympic Village, a melting pot of athletic bodies.

The disease's symptoms include fever, rash, redness of the eyes, muscle and joint pain, malaise and headaches. Cases generally last from two days to a week, but for athletes who have trained for four years or more to compete in a narrow window of opportunity, any time lost is monumental.

Of greater concern is a birth defect linked to the Zika virus. Babies born with microcephaly suffer small heads, and development of their brains is stunted, according to doctors. In Brazil, researchers found babies with the condition whose mothers reported symptoms of Zika during their pregnancies.

The situation is being taken seriously beyond medical circles. In an exclusive report, Reuters said United States Olympic Committee officials held a conference call with representatives of U.S. sports federations to discuss the virus and the Games, which are scheduled for Aug. 5-21. The USOC informed the federations that if any athletes or staff wished to avoid traveling to Brazil, they should be allowed to remain at home.

The USOC's primary focus was on pregnant women and those considering becoming pregnant, but its allowances cover all athletes and staff, Reuters reported. Kenya indicated that it may keep its teams home from the Games, a significant decision for a nation that boasts a legacy of world-renowned distance runners. Great Britain has briefed its athletes about the virus, but hasn't altered its plans to attend the Games.

For its part, Brazil is being proactive to the Zika threat, particularly in regard to the Olympics. Troops have treated standing water to stem mosquito activity. The nation's annual Carnival, which began last weekend, didn't appear to be slowed by the threat, with many of the costumed revelers making light of the outbreak.

Zika is only the latest stumble for Brazil, the first South American country awarded the Olympic Games. Besides an economy that's suffering a deep recession, Brazil has been damaged by a government corruption scandal. Olympic organizers have had to scale back seating at some venues, and they continue to deal with contamination in the water where rowing, swimming and sailing events are scheduled to be held.

That leaves the country desperate to reach the finish line with its troubles before the Games can begin.