HEALTH

Zika Is Flying Into The US—And Airports Have No Way To Stop It

Of the more than 500 cases of the Zika virus on US soil documented so far, all are from people flying into the U.S.

HEALTH
Illustration: Diana Quach
May 25, 2016 at 3:38 PM ET

Almost every single Zika case in the U.S. so far has been contracted overseas and walked through an American airport onto American soil. And while the rate of incoming human Zika carriers is likely to shoot up this summer, there’s nothing airports can do about it. Our first line of defense is, in this case, no defense at all.

A new report from the PLOS Journal shows how airline travel is likely to play a significant role in the transmission of the Zika virus. For most of Zika’s journey around the world, humans in airplanes will be the main vector, making airports the silent hubs for 2016’s most troubling public health problem.

The virus is, in most cases, transmitted from infected humans to new hosts by the Aedes aegypti or Aedes albopictus mosquito. They’re only native to limited regions within the continental U.S. The small number of people living in the contiguous U.S. who have been infected thus far have almost all been infected overseas and brought their infection home with them. The Centers for Disease Control and Prevention has counted 544 cases of Zika virus disease within the U.S. to date, all of which have been deemed “travel-associated cases.” The CDC defines this as travelers returning from affected areas, their sexual contacts, or infants infected in utero. While most of these transmissions appear to be the result of direct travel, the Zika virus can be sexually transmitted. This has occurred just 10 times since 2015.

As summer (mosquito season) approaches, fears are on the rise that human-to-human infection will become a reality for mosquito-heavy areas in the U.S.

“It will be more likely that local Zika virus transmission could occur during the warm months because conditions are more favorable for mosquitoes and because humans spend more time outdoors,” Andrew Monaghan, an atmospheric scientist and one of the study’s researchers, told Vocativ in an email.

But for that to happen, there needs to be a lot more Zika carriers walking about. And before they end up walking the streets of your area, they’re going to walk off a plane arriving from a Zika-prone country, and through an airport. Carriers may be asymptomatic, and Zika’s benign flu-like symptoms are hard to differentiate from other relatively mild conditions, so airport monitoring probably won’t work. As it’s not contagious it won’t spread in the environment of the airport either, making heightened vigilance there even more pointless. All authorities seem able to do is educate anyone who does have the disease on how not to spread it sexually, and advise them to stay away from mosquitoes. Or (and this will never happen) they could just ban travel from affected countries altogether.

We looked at patterns of commercial airline flights entering or reentering the U.S. from countries with CDC Zika travel notices using 2014 data from the Bureau of Transportation Statistics. That told us which airports were likely to welcome the most travelers from Zika-affected countries during the summer months of 2016.

The diagram is based on 2014 figures, so there is likely to be some change based on events like the Rio Olympics, but Miami International Airport is likely to have the highest number of travelers arriving from countries where Zika transmission is ongoing this summer. Miami was also deemed the most at-risk city in the PLOS report due to a combination of traveler inflows and mosquito prevalence. 21 percent of all reported Zika cases in the U.S. so far have been in Florida. According to the Florida Department of Health, there are nine pregnant women known to have Zika in the state. Further north, John F. Kennedy Airport in New York also sees high rates of travelers from countries where Zika is present. New York is home to another 21 percent of all of America’s current Zika cases, all of which are travel-related, but New York’s climate means lessens the risk level for local transmission.

“The highest risk areas for Zika in the U.S. would be areas where Aedes aegypti exists, there is high potential for travel-related introduction of the virus, and there is high human exposure,” Monaghan said. “These areas coincide with counties in southern Florida and southern Texas where we have previously had dengue and chikungunya transmission.”

Despite this, it’s the infected people rather than those that might be affect who are the worry. “In this case, airports are a mechanism from one place to another,” said Dr. Nicky Cohen with the CDC’s Division of Global Migration and Quarantine. “We’re more worried more about infected people rather than infected mosquitoes or contamination at the airplane or airport itself.”

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None of the specialists Vocativ spoke to seemed concerned with human-to-human transmission (by mosquitoes or otherwise) in the U.S. “Most authorities think that the transmission, if it occurs, will be relatively modest and contained to small geographic areas,” Monaghan said.

Even Amir Attaran, a professor of law and medicine at the University of Ottawa who said in the Harvard Public Health Review that the Olympics should be cancelled because of how it might accelerate the global spread of Zika, maintained that America’s Zika risk is not worth any kind of drastic measures.

“Sure, the U.S. is going to see sporadic cases, the U.S. is probably still going to have a handful of microcephaly cases,” he said. “But the emphasis is on ‘handful.’ Basically, because we all lived in screened homes and we’re outside not all that much and the mosquito season isn’t that long, it’s just not likely to establish local transmission.”

Other countries, however, aren’t so well equipped, and have a much greater problem with the mosquito-borne element of the transmission chain.

“It’s a totally different game for Ethiopia or Nigeria,” said Attaran. “That would be a very interesting analysis.”

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The World Health Organization, however, has advised against travel bans, which would be indiscriminate, instead recommending that aircrafts and airports are disinfected to its standards. They also recommend that travelers headed for areas with Zika transmission receive up-to-date advice on risk measurement and management, and that pregnant women and their sexual partners take necessary precautions.

The CDC has decided against a travel warning or recommending that airports spray airplanes with pesticides, instead focusing its attention on ensuring that travelers are educated about risks via posters for travelers as they go through security.

Andrew Huff, the associate vice president of EcoHealth Alliance, which regularly forecasts airports at risk of receiving passengers with confirmed cases of Zika, also told USA Today that while we can assess the risk, “there’s not much individuals can do with this information.”