New map details threat of Zika worldwide, including Europe and U.S.

LAWRENCE — Accounting for a host of often-overlooked drivers of transmission, team of researchers headquartered at the University of Kansas has plotted the Zika risk around the world with unprecedented resolution.

• The mapping effort uses “ecological niche modeling,” often used to predict the distribution of various species, to show the virus’ powerful potential to spread in South and Central America.
• In the meantime, Sub-Saharan Africa, Australia, Melanesia and parts of New Zealand also face substantial jeopardy from Zika.
• This is the first map to place Europe at risk of Zika virus transmission.
• The findings also suggest that scattered parts of the southern U.S. — including Florida, Texas and Louisiana — show public-health vulnerabilities from the virus.

“It’s the first detailed map of transmission across the world, not just in a single country,” said Abdallah Samy, who headed the research prior to earning his doctorate this May from KU's Biodiversity Institute. “We use different combinations of variables to see what are the major divers — such as climate, or socioeconomics or people’s ability to access certain areas — and in the final map we merge the all variables.”

The resulting map predicts the likelihood of Zika exposure in the coming years by segmenting Earth’s landmasses into squares of five-by-five kilometers each, and crunching the numbers for each of them.

Because the virus can spread through contact with the Aedes mosquito, and also person-to-person via sexual contact, blood transfusions and mother-to-child during pregnancy, multiple factors influence risk assessment.

“For each area, we asked ‘is it mosquito exposure, climate or socioeconomic variables like accessibility for people to get into an area where Zika is endemic and then potentially spread the virus through travel?’” said Samy. “In Europe, the major transmission risks are socioeconomic. But in Brazil, it’s mosquitoes, the climate and socioeconomic factors — the same situation for other parts of the world that are at high risk.”

The findings recently were posted to the Zika Fast Track site and published in Memórias do Instituto Oswaldo Cruz, an international journal of biological and biomedical research based in Brazil, where the current outbreak has been centered since 2015. While peer-review is still underway on the results, the severity of the Zika outbreak necessitated publication prior to the completion of that process.

“This map can be used by public health officials and international organizations that combat disease,” Samy said. “It’s also intended for the public. If you’re going to travel to a specific area in Brazil, and you know it’s a risk area for Zika, you should consider how to reduce the chances of transmission with clothing or insect repellant.”

Samy’s co-authors were KU’s A. Town Peterson, Stephanie M. Thomas of the University of Bayreuth in Germany, Ahmed Abd El Wahed of Georg-August University in Germany and Kevin P. Cohoon of the Mayo Clinic.

Samy said the course of the outbreak thus far is similar to what his team’s map predicts with a high degree of specificity.

“We have multiple dimensions in our models, and in addition we use a very accurate algorithms that account for bias,” he said. “So far, we haven’t found any cases that don’t conform with our model.”