Zika Virus Transmission Risk During Olympics Is Low, CDC Says Olympics travel is a fraction of overall travel to Zika-affected countries.

 -- The risk of Zika virus transmission during the upcoming Olympic games in Rio will be low due to colder weather, the U.S. Centers for Disease Control and Prevention said today.

In a new risk-assessment report, the CDC found that since the games are occurring during winter in Brazil, the cooler, drier weather will reduce mosquito populations, thus lowering the chance of Zika transmission to visiting athletes and spectators.

Additionally, the agency found that even though there will be increased travel to the area for the Olympics, the overall risk of the virus being transmitted to new areas due to Olympics-related travel is low. The estimated 350,000 to 500,000 international visitors and athletes from 207 countries who are expected to travel to Rio de Janeiro for the 2016 Olympic and Paralympic Games represent a tiny fraction -- 0.25 percent -- of total travel to and from Zika-affected countries, according to the CDC report.

CDC Director Tom Frieden addressed the report today, telling reporters there wasn't a large "public health reason to delay or change the games."

"Compared with all travel to Zika-endemic areas, the Olympics account for about one-tenth of 1 percent of travel from the U.S. and globally about one-quarter of 1 percent, so even if Olympics didn’t exist, 99.75 percent would be the same risk," he said.

Surprisingly, the agency found residents from four countries -- Chad, Djibouti, Eritrea and Yemen -- have a "unique" risk if they attend the games. People in those areas did not have significant travel to any areas with ongoing Zika transmission, but lived in areas where the mosquitoes that spread Zika are likely to flourish, the CDC found.

The CDC continues to advise all pregnant women to avoid travel to any areas with ongoing Zika transmission due to the risk of birth defects and that others should take steps to protect themselves.

"Athletes and visitors to Rio de Janeiro and other Zika transmission areas should follow precautions to prevent exposure to the virus," the report authors said. "Specifically, all delegation members and visitors should take rigorous steps to reduce the likelihood of mosquito bites."