The Potential Impacts of 21st Century Climatic and Population Changes on Human Exposure to the Virus Vector Mosquito Aedes aegypti

The mosquito Aedes (Ae). aegypti transmits the viruses that cause dengue and chikungunya, two of the most important vector-borne viral diseases globally. We investigate how choosing alternate emissions and/or socioeconomic pathways may modulate future human exposure to Ae. aegypti. Occurrence patterns for Ae. aegypti for 2061-2080 are mapped globally using empirically downscaled air temperature and precipitation projections from the Community Earth System Model, for the Representative Concentration Pathway (RCP) 4.5 and 8.5 scenarios. Population growth is quantified using gridded global population projections consistent with the Shared Socioeconomic Pathway (SSP) storylines SSP3 (“Regional Rivalry”) and SSP5 (“Fossil-fueled Development”). Change scenarios are compared to a 1950-2000 reference period assuming year 2000 population. The annual average number of people exposed globally to Ae. aegypti for the reference case is 3794 million, a value projected to statistically significantly increase by 8-12% by 2061-2080 if only climate change is considered, and by 127-134% (SSP3) and 59-65% (SSP5) if both climate and population change are considered (lower and upper values of each range are for RCP4.5 and RCP8.5 respectively). Thus, reduced anthropogenic climate change resulting from taking the RCP4.5 emissions trajectory instead of RCP8.5 may mitigate future human exposure to Ae. aegypti globally, but the effect of population growth on exposure may be roughly 5-15 times larger. Regionally, Australia, Europe and North America are projected to have the largest percentage increases in human exposure to Ae. aegypti resulting from climate change alone. Future exposure to Ae. aegypti will likely depend on emissions and socioeconomic pathways taken.