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The World Health Organization will not urge the International Olympic Committee to postpone or move this summer’s Rio Games because of the Zika outbreak in Brazil.

Holding the Olympics as scheduled won’t substantially increase the risk of the Zika virus spreading, a committee of experts that advises the WHO on Zika told the global health agency on Tuesday.


“The committee concluded there … is very low risk of additional international spread from the Olympics,” said Dr. David Heymann, who chairs the expert panel. A former assistant director general at the WHO, Heymann is a professor at the London School of Hygiene and Tropical Medicine.

Twenty percent of the world’s population is already living in places where the Zika virus is spreading and 30 percent of global travel involves transit in and out of those countries, said Dr. Bruce Aylward, the WHO’s executive director for outbreaks and health emergencies.

The WHO accepted the committee’s advice that no general restrictions on travel are warranted, but reiterated earlier calls for pregnant women not to visit places where Zika is spreading.


The committee also recommended that Brazil be encouraged to continue in its efforts to control mosquito populations around Olympic event venues and to make certain there is enough mosquito repellent— and, given that Zika can be transmitted sexually, enough condoms — for both athletes and visitors.

At least 227 academics have signed a petition arguing that it’s unsafe to hold the Olympics and Paralympics in Rio this summer.

A leader of that effort, bioethicist Arthur Caplan from NYU School of Medicine, called the WHO’s decision “a gamble.”

“They are betting on the weather, responsible behavior by visitors, and a low sexual transmission rate,” Caplan told STAT. “So this means each person will have to make an ‘informed choice’ about going.”

But international health law expert Lawrence Gostin applauded the decision.

“The risk of holding the Olympic games is lower than the risk of canceling or postponing the games due to the economic and political turmoil it would cause in Brazil,” said Gostin, a professor at Georgetown University and director of the World Health Organization’s collaborating center on public health law and human rights.

Tuesday’s meeting was the third for the Zika emergency committee — a panel of outside experts which advises the WHO on its response to the outbreak.

Based on its advice, WHO Director-General Dr. Margaret Chan declared Zika a global health emergency earlier this year.

The virus is mainly spread by mosquitoes, but an infected person can also transmit it to a partner during sex. The virus causes birth defects in some infants born to women infected during pregnancy. And it can trigger a form of progressive paralysis called Guillain-Barré Syndrome. The condition normally reverses itself, but can be fatal in some cases.

Scientists are still struggling to determine how often infection in pregnancy leads to birth defects in the fetus. But as time passes, increasing numbers of cases of microcephaly — an abnormally small head and underdeveloped brain — and an array of other birth defects are being reported by countries with Zika outbreaks.

One puzzling situation though, is that of Colombia. Though it has had thousands of infections in pregnant women, the WHO says Colombia has reported only seven cases of microcephaly. Brazil has reported 1,551.

Aylward said that seeming discrepancy has been a concern for both the WHO and its regional office for the Americas, the Pan American Health Organization.

“In fact, our regional director has been in discussion with the [health] ministry in Colombia as well as our technical staff to try and understand and reconcile this,” he said.

One potential explanation, Aylward said, is that other countries are reporting all cases where microcephaly is seen, even if it appears in a miscarried or aborted fetus. Colombia, on the other hand, is only reporting microcephaly when a baby is born with the condition.

Reporting live births only will downplay the situation, he suggested, acknowledging the WHO is hearing that some women — he did not say in which countries — are choosing to terminate pregnancies if they learn they are carrying a fetus with microcephaly.

This story has been updated with additional information from the WHO.