On June 14, the World Health Organization reiterated that the Zika outbreak did not pose enough riskto warrant moving, postponing, or cancelling the summer Olympics in Rio. “The risk is already low. There is very low risk of further international spread from the Olympics,” said David Heymann, chair of the WHO’s emergency committee on Zika.

The decision comes after more than 200 academics, many of them ethicists, signed an open letter asking the WHO to consider postponing or canceling the Olympics due to the mosquito-borne virus. The WHO still considers Zika a public health emergency because of its link to microcephaly. But if you drill down into the details about Zika, you can see why scientists and officials with specific knowledge of Zika don’t think the virus will be a big deal at the games.

The exception, of course, is for pregnant women. Both the WHO and the US Centers for Disease Control and Prevention recommend pregnant women do not travel to dozens of countries where Zika is actively circulating. But for everyone else, here’s why the risk from Zika is minimal.

__August is winter in Brazil __

Yes, it’s technically the summer Olympics, but Brazil is in the southern hemisphere where August means winter. (It will be only the third time the summer Olympics are held in the southern hemisphere and the first time in South America.) Mosquito-borne viruses like Zika follow a fairly predictable seasonal pattern: The insects thrive when it is wet and warm. In contrast, August is one of Rio’s coolest and driest months.

In fact, says Scott Weaver, a mosquito-borne virus expert at the University of Texas Medical Branch, Zika is more likely to be circulating then in Central America and the Caribbean, where August is still mosquito season. It doesn’t make sense to zero in on Olympics-related travel this summer. That gets to the next point.

__Millions of people are already traveling in and out of areas with Zika __

“You have to consider traffic from an entire affected area. There are millions and millions of people,” says Alessandro Vespignani, a disease modeling researcher at Northeastern University who is working on modeling how Zika spreads. “The addition to the risk with the Olympics is extremely small.” The Olympics will account for only 1 or 2 percent of all air travel to Zika-affected regions, estimates Vespignani. In past years, the Olympics have displaced other tourists, who decide to avoid the crowds and high prices of the games.

Travel has already spread Zika. The US has had over 200 cases of travel-related Zika in pregnant women this year. Unless travel bans for the general population are also on the table—and they have no reason to be at this point—canceling the Olympics alone won’t make a big difference.

__Nobody is trying to cancel the Olympics because of dengue __

Zika isn’t the only mosquito-borne virus in Brazil, and unless you’re pregnant, it’s far from the most serious. “If I were planning to go to the Olympics, I’d be more worried about dengue and chikungunya,” says Weaver. Both of these disease are far more dangerous to healthy adults.

Chikungunya made it to South America for the first time just before the World Cup in Brazil, and nobody seriously talked about canceling the World Cup. “We've had dengue circulating uncontrolled in the Americas for decades, with plenty of sports and international events, and people didn’t consider canceling those events,” says Weaver. If the levels of chikungunya and dengue in North America are any indication, Zika won’t spread rapidly either.

__Moving the Olympics would be logistically impossible __

Cities have ten years to get ready to host the Olympics, and they need all those years. Not counting the spectators, the summer Olympics might involve 17,000 athletes and trainers, 25,000 managers, and 70,000 volunteers—each of whom need some combination of food, beds, toilets, and buses. “It’s not turn on a dime infrastructure,” says Harvey Louie, who was a logistics manager for the 1996 Atlanta Olympics. The summer games are due to start in four weeks.

Moving that mass of people to, say, venues in 2012’s host city London, would mean bumping dozens of other events that have also been scheduled years in advance. One of the most difficult events to plan, says Louie, is the marathon. It involves closing roads, each of which could require approval of the city, homeowners, and business owners. And that’s just one of 42 sports. “You just couldn’t move the Olympics,” he says. Cancelling it means reneging on millions of dollars of sponsorships, and preventing athletes who have spent years training from competing.

Of course, none of this is an argument against cancelling the Olympics in a true public health emergency. But every decision comes with costs, and the risks of Zika don’t rise high enough to make it worth disrupting the Olympics. If Zika were so dangerous that the Olympics has to go, then so should all nonessential travel. That’s just not true for now.