Here's How Many Rio Olympics Visitors Will Contract Zika Virus

Public health workers fumigate stadiums in Rio de Janeiro in January 2016 to prepare for Carnaval celebrations. Christopher Simon/AFP/Getty Images

When the Olympic Games kick off next week in Rio de Janeiro, the Brazilian city will see an influx of up to 500,000 visitors, tourists, vendors, athletes and media workers. Worries have spread about the state of things in Rio these days, from still-under-construction athlete housing to uncommonly polluted water. One of the most high-profile concerns has been the spread of Zika virus.

Aedes aegypti mosquitos that carry the virus can transmit them to humans through a bite, and Zika also can be transmitted between people through sexual contact. In January, the World Health Organization (WHO) declared Zika a global public health emergency.

But according to a new study from researchers at the Yale School of Public Health, the Zika virus may not be quite as scary as all the press it's gotten — at least not in Brazil, at this time, for these visitors. The study, published online in Annals of Internal Medicine, says that in a worst-case scenario, we should expect to see between three and 37 Zika infections among those coming to Rio.

“It's important to understand the low degree of risk posed by the Olympics in the scheme of many other factors contributing to international Zika virus spread,” says Joseph Lewnard, a doctoral candidate and the paper's lead author, in a press release.

The scientists used mathematical models to take into account infection rates, seasonal conditions and travel patterns, among other data. It's also likely that visitors would experience better conditions than the vast majority of locals, but the researchers took the worst-case scenario and assumed the entire visiting population had it just as bad as those who lived in Brazil.

And while there've been those who've argued for the cancellation, postponement or relocation of this year's Olympics, the official word from WHO is that doing so would have a negligible effect on the spread of Zika (ZIKV) — and that even pregnant sports fans can safely attend the games with a few precautions in mind.

"The magnitude of ZIKV risks attributable to the Olympics should be interpreted in the context of all opportunities for the virus to spread internationally," the researchers write in the study. "Aside from the Olympics, Brazil receives more than 6 million international arrivals annually, whereas the Caribbean region hosts nearly 30 million visitors annually and may encounter seasonal increases in ZIKV transmission risk during the summer."