Global expansion and redistribution of Aedes-borne virus transmission risk with climate change
Authors: Ryan Sadie J. , Carlson Colin J. , Mordecai Erin A. , Johnson Leah R. 
Published: August 2017

Forecasting the impacts of climate change on Aedes-borne viruses—especially dengue, chikungunya, and Zika—is a key component of public health preparedness. We apply an empirically parameterized model of viral transmission by the vectorsAedes aegyptiandAe. albopictus, as a function of temperature, to predict cumulative monthly global transmission risk in current climates, and compare them with projected risk in 2050 and 2080 based on general circulation models (GCMs). Our results show that if mosquito range shifts track optimal temperature ranges for transmission (21.3 – 34.0°C forAe. aegypti;19.9 – 29.4°C forAe. albopictus), we can expect poleward shifts in Aedes-borne virus distributions. However, the differing thermal niches of the two vectors produce different patterns of shifts under climate change. More severe climate change scenarios produce larger population exposures to transmission byAe. aegypti, but not byAe. albopictusin the most extreme cases. Climate-driven risk of transmission from both mosquitoes will increase substantially, even in the short term, for most of Europe. In contrast, significant reductions in climate suitability are expected forAe. albopictus, most noticeably in southeast Asia and west Africa. Within the next century, nearly a billion people are threatened with new exposure to virus transmission by bothAedesspp. in the worst-case scenario. As major net losses in year-round transmission risk are predicted forAe. albopictus, we project a global shift towards more seasonal risk across regions. Many other complicating factors (like mosquito range limits and viral evolution) exist, but overall our results indicate that while climate change will lead to increased net and new exposures to Aedes-borne viruses, the most extreme increases inAe. albopictustransmission are predicted to occur at intermediate climate change scenarios.

Author Summary

The established scientific consensus indicates that climate change will severely exacerbate the risk and burden of Aedes-transmitted viruses, including dengue, chikungunya, Zika, and other significant threats to global health security. Here, we show more subtle impacts of climate change on transmission, caused primarily by differences between the more heat-tolerantAedes aegyptiand the more heat-limitedAe. albopictus.Within the next century, nearly a billion people could face their first exposure to viral transmission from either mosquito in the worst-case scenario, mainly in Europe and high-elevation tropical and subtropical regions. However, while year-round transmission potential fromAe. aegyptiis likely to expand (particularly in south Asia and sub-Saharan Africa),Ae. albopictustransmission potential is likely to decline substantially in the tropics, marking a global shift towards seasonal risk as the tropics eventually become too hot for transmission byAe. albopictus.Complete mitigation of climate change to a pre-industrial baseline may protect almost a billion people from arbovirus range expansions; however, middle-of-the-road mitigation could produce the greatest expansion in the potential for viral transmission byAe. albopictus. In any scenario, mitigating climate change would shift the projected burden of both dengue and chikungunya (and potentially otherAedestransmitted viruses) from higher-income regions back onto the tropics, where transmission might otherwise begin to decline due to rising temperatures.