CDC Finds Olympics Unlikely to Raise Risk of Spreading Zika Virus

The analysis pinpointed which countries faced an elevated risk of spreading Zika just based on anticipated travel by athletes and delegates to the Games in Rio de Janiero.

With the 2016 Summer Olympic Games quickly approaching, there’s great concern about the threat of infection and disease transmission from the mosquito-borne Zika virus for those traveling to and from Rio de Janeiro, Brazil. However, the threat may not be as alarming as one might think.

A report issued today by the CDC found that an increased risk of Zika virus transmission as a direct result of attending the Games is unlikely, with estimated travel to the Games representing less than .25% of total travel to all Zika-affected countries. The report’s authors noted that Rio de Janeiro will be in its winter months when cooler, dryer weather generally reduces mosquito populations, which is likely to help decrease the risk of transmission.

Researchers conducted a risk assessment that studied all 206 countries participating in the Olympic Games and the number of individuals set to take part as of June 30, 2016. They assessed which countries are specifically at an increased risk for Zika transmission by employing an elimination process with 5 core qualifiers, including whether the country has a CDC travel notice, a history of the disease, or an environment that could support transmission of the disease.

Of the participating 206 countries, 39 countries have current CDC travel notices for ongoing Zika virus outbreaks or epidemics and were therefore not considered at an increased risk. Of the the remaining 167 countries without a CDC warning, 148 were also taken out of consideration for potential risk due to either the country’s history of previously having the disease or the inability of its environment to foster the disease’s transmission.

This elimination process left only 19 countries that had the potential to encounter high risk with the Zika virus. For 15 of these remaining countries that are sending athletes to Rio de Janeiro in the coming month, the study found that the risk of Zika infection would not be substantially higher than what would occur anyway, based on that country’s usual aviation travel baseline.

Therefore, the CDC research team were left with 4 countries—Chad, Djibouti, Eritrea, and Yemen—that do not have a substantial amount of travel to any country around the globe with local Zika transmission, except for their athletes’ upcoming trip to the Olympic Games. Researchers suggested that only these 4 countries of the total 206 attending the Olympic Games may be at an increased risk for Zika transmission. However, these 4 countries combined will be represented by only about 19 athletes and 60 delegates, which is a small fraction of the 350,000 to 500,000 people expected to attend the event.

“With the exception of 4 countries, attendance at the Games does not pose a unique or substantive risk for mosquito-borne transmission of Zika virus in excess of that posed by non-Games travel,” the authors wrote in the report. “Efforts to enhance global health security to prevent, detect, and respond to Zika virus, as well as other emerging infections, require a sustained international commitment at all levels of government, the private sector, and civil society.”

The authors added that individuals should still remain vigilant in protecting themselves from the virus. Pregnant women are still advised not to travel to areas with an ongoing Zika epidemic, and those attending the Games should come prepared with insect repellant and wear long sleeves and pants wherever possible.


Grills A, Morrison S, Nelson B, Miniota J, Watts A, Cetron MS. Projected zika virus importation and subsequent ongoing transmission after travel to the 2016 Olympic and Paralympic Games — Country-Specific Assessment, July 2016 [early release July 13, 2016]. MMWR. 2016;

Related Videos
Screenshot of Sancy Leachman, MD, PhD, smiling
Jeremy Wigginton, MD
Screenshot of Eva Parker, MD, smiling during an interview
Screenshot of Eleonora Lad, MD, PhD, smiling
Davey B. Daniel, MD, Chief Medical Officer, OneOncology
© 2023 MJH Life Sciences
All rights reserved.