Research Briefs

1.3B people could be exposed to Zika virus by mid-century

Nov. 20, 2020: A warming world will shift arboviruses, such as Zika virus, into new areas where human populations are susceptible to infection.

1.3B people could be exposed to Zika virus by mid-century

Digitally-colorized transmission electron microscopic image of Zika virus, image by Cynthia Goldsmith and available on the CDC Public Health Image Library (ID 20541). 

Even before the 2015 Zika pandemic subsided, researchers recognized the links between a warming world and arboviruses shifting their ranges into new areas where human populations are susceptible to infection. UF medical geographer and EPI faculty member Sadie Ryan is the first author of a new study recently published in Global Change Biology that uses a temperature-dependent transmission model to show how Zika virus may expand globally to reach 1.33 billion new potential hosts in a scenario of unmitigated climate change. But if the effects of projected climate change are lessened through mitigation efforts to moderate emission scenarios, some 300 million of these people may be protected.

The net difference in how many people may be at risk of Zika virus is large because while there are vast geographic areas where the climate will become newly suitable for the mosquitos that carry this virus, there are few regions that will grow too hot for these insects in the future. In the map below, the researchers show months with temperatures suitable to Zika virus transmission. The darkest blue represents the change in an additional month per year with suitable temperatures while dark red indicates all 12 months will be suitable. Panel (a) models a moderate climate change scenario and panel (b) models an unmitigated climate change scenario.

A temperature range map showing Zika transmission suitability

North America and Europe are the geographic areas where populations will be most vulnerable to an expanded range for Zika virus. Because the risk of infection would still affect so many people, even if emissions were to be lowered now, the researchers call for a focus on evaluating the immune history of vulnerable populations to better predict where the next Zika virus outbreak may occur. The blister map below depicts proportional red circles that represent the size of regional populations, measured in the millions, at risk under a moderate climate change scenario, panel (a), and under an unmitigated climate change scenario, panel (b).

Blister map showing relative scales of populations at risk of Zika by 2050

Read more

Ryan, SJ. Carlson, CJ., Tesla, B., et al. "Warming temperatures could expose more than 1.3 billion new people to Zika virus by 2050." Global Change Biology, 2020; 00:1–10. https://doi:10.1111/gcb.15384

Read Sadie Ryan's EPI profile.

Written by DeLene Beeland