Michael Phelps will be the bearer of the U.S. flag during the Friday night ceremony at Maracana Stadium, selected in a vote by all members of the American Olympic team.
Golfer Rory McIlroy became one of the most high-profile sports stars to opt out of the Rio de Janeiro Olympics because of concerns about the Zika virus, saying Wednesday it is "a risk I am unwilling to take."
The World Health Organization says there is "no public health justification" for postponing or canceling the Rio de Janeiro Olympics because of the Zika outbreak.
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