Experts Study Risks of Zika Virus Spreading at Rio Olympics

RIO DE JANEIRO: With about 500,000 people expected to visit Brazil for the Olympics here this year, researchers are scrambling to figure how much of a risk the Games might pose in spreading the Zika virus around the world.

Infectious disease specialists are particularly focused on the potential for Zika to spread to the United States. As many as 200,000 Americans are expected to travel to Rio de Janeiro for the Olympics in August. When they return to the Northern Hemisphere and its summer heat, far more mosquitoes will be around to potentially transmit the virus in the United States.

Brazilian researchers say they believe that Zika, which has been linked to severe birth defects, came to their country during another major sports event - the 2014 World Cup - when hundreds of thousands of visitors flowed into Brazil. Virus trackers here say that the strain raging in Brazil probably came from Polynesia, where an outbreak was rattling small islands around the Pacific.

As many as 1.5 million people are believed to have contracted the virus in Brazil since then, and the authorities are now investigating thousands of reported cases of babies being born recently with brain damage and abnormally small heads. Zika has spread to more than 20 nations and territories in the Western Hemisphere, according to the World Health Organization, illustrating how quickly the epidemic can expand even without a big international gathering.

By itself, the virus is not normally life-threatening, and most people who become infected have no symptoms at all.

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The big question is whether Zika is responsible for the huge increase in birth defects reported by doctors, hospitals and other medical officials in Brazil over the last few months. That connection has still not been proved.

"There is more and more concern that there may be a causal relationship, but a lot of the work so far is to rule out other possible causes," Dr. Bruce Aylward, an assistant director general at the WHO, said on Thursday, adding that it might take six to nine months to know for sure.

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Asked whether the WHO would advise people not to travel to Brazil for the Olympics, he replied: "I would think that would be very, very unlikely."

U.S. officials said Thursday that there was little likelihood of a Zika outbreak in the United States, adding that the country's long history of mosquito control efforts had curbed other mosquito-borne diseases, like dengue or chikungunya, in the past.

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But because the virus can be carried in a person's blood to a new country, then passed to others by mosquito bites, researchers are trying to determine whether a big global event like the Olympics could add to the global transmission of the disease.

"Infected travelers departing from Brazil are expected to return to regions that have the potential to sustain transmission," said Moritz Kraemer, a scholar at Oxford University who researches the global spread of viruses, emphasizing that many travelers would return to their home countries during the summer. "So the international spread of the virus might increase substantially due to higher activity of mosquitoes."

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Using worldwide temperature profiles and air travel routes, Kraemer and other researchers found that more than 60 percent of the population of the United States lives in areas where Zika can be transmitted during the Northern Hemisphere's summer, when the Games will be held. A much smaller number, about 23 million people, live in parts of the United States where Zika can be transmitted year-round, like Florida and Texas, the researchers found.

In the Southern Hemisphere, by contrast, it is summer right now, and mosquitoes are rapidly spreading the disease in Brazil and other warm parts of Latin America and the Caribbean.

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That may pose a particular risk for big events like Brazil's Carnival, which goes into full swing next month, but Olympics officials emphasize that it will be winter in Rio when the Games are held, which could limit the spread of mosquito-borne diseases.

Even so, Brazilian virologists contend that mosquitoes can still easily transmit viruses in Rio and other tropical cities year-round, pointing out that Zika may have begun spreading in Brazil during its winter in 2014.

Brazil has been one of the hardest-hit countries and the authorities are under intense pressure domestically to contain the Zika epidemic right away, regardless of the Olympics.

Mario Andrada, a spokesman for the Rio Olympics organizing committee, said that there had been no discussions about canceling the Games or moving them to another city because of Zika.

He added that teams were reviewing Olympic venues daily to eliminate problems like stagnant water where mosquitoes can breed. He said officials were also seeking to work on the "psychological aspect" of athletes being fearful about getting Zika by guaranteeing a supply of mosquito repellent and by keeping teams from every nation informed about the virus.

"The risk is no joke, so we will maintain this inspection program until the end of the Paralympics," Andrada said, referring to the multisport event that will be held in September, after the Olympics.

Some Brazilian virus specialists contend that the measures adopted by Olympic officials are meager given the scope of the Zika epidemic in Brazil. Beyond the risk to infants, hundreds of people around the country have been stricken by Guillain-Barré, a syndrome that Brazilian officials warn may be connected to Zika and can leave patients paralyzed for weeks.

"It's a step in the right direction to inspect facilities, but this is something that should have been done on a broader basis five years ago, not just in the months before the Games," said Carlos Granato, an infectious diseases specialist at the Federal University of São Paulo. "Mosquitoes persist in a multitude of areas around Rio and other Brazilian cities, so simply keeping Olympic venues free of them is not enough."

The fears over Zika are merely the latest challenge to the Rio Olympics. Sailors have complained angrily about competing in the city's sewage-infested bay. Prosecutors have asserted that builders paid bribes to win contracts for Olympic venues. Clashes have broken out over evictions to make way for Olympic projects. Deep spending cuts have come as Brazil reels from its worst economic slump in decades.

"Plagued by so many problems, Rio is clearly in a league of its own among host cities of the Olympics in recent memory," Andrew Zimbalist, a scholar who specializes in sports economics at Smith College, said.

While ticket sales had already been disappointing organizers, concerns are growing that travelers from the United States and other countries could cancel plans to visit because of Zika.

"People have called to ask, 'If this explodes, how would I cancel my trip?'" said Anbritt Stengele, president of Sports Traveler, a company in Chicago which specializes in travel packages for major sporting events. She said that about 15 percent of her clients who had booked trips for the Olympics had called in recent days to ask about the Zika virus and the possibility of modifying their trips.

"It's a tricky situation for us, because everything is paid for in advance - airfare, hotels, ground transportation," Stengele said. She said most of the vacation groups traveling to the Summer Olympics include women and families with children.

"This is a completely different demographic," she said, compared with the largely male tourists who attended the 2014 World Cup. "The Olympics is about families."

Virologists are trying to piece together how the virus began spreading in Brazil, and where it might go from here.

Dr. Felipe Scassi, a researcher at the University of São Paulo's Tropical Medicine Institute, said that an Asian strain of Zika appeared to have made its way here from Easter Island, a part of Polynesia controlled by Chile, during the World Cup. After spreading in northeast Brazil, Zika was found in neighboring Suriname and is now being transmitted up and down Latin America and the Caribbean.

Despite the rapid spread of the virus, Scassi said that the epidemic could look different in Brazil a few months from now.

"The colder temperatures should diminish populations in various cities, including Rio," he said. "The risk in relation to Zika during the Olympics will still exist, but it will be a lower risk than now."

Now athletes and fans alike are trying to determine whether it makes sense to travel to Rio. Alysia Montaño, an American runner who competed at the U.S. Track and Field Championships while eight months pregnant, said the Zika virus could affect her decision to bring her young daughter, who will turn 2 in August, to the Games.

"The greatest thing is that I will not be a pregnant woman at the Olympics," said Montaño, who is hoping to compete in Rio. "Having my daughter there is really, really important to me, but I'll need to consider if she'll be a spectator at home or at the Games themselves."