The World Health Organization is to examine the risks of holding the Olympics in the Brazilian city of Rio de Janeiro because of the Zika virus.
US Senator Jeanne Shaheen wants to know whether the Rio Games could accelerate the spread of the mosquito-borne virus.
"The Olympics draw people from all over the globe," she said. "It's important we understand the health implications."
On Wednesday, Northern Ireland golfer Rory McIlroy said his concerns about the virus had eased.
However, fellow golfers Vijay Singh and Marc Leishman have already announced they will not be going to the Olympics because of the virus, which is linked to brain defects in newborn babies.
American cyclist Tejay van Garderen, whose wife is pregnant, says he will not compete in Rio because of concerns about Zika.
WHO said it planned to hold another emergency committee meeting in June, when it would discuss the Olympics, and added it would make its report public.
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