Modeling the Seasonal Risk of Aedes aegypti Transmitted Viruses under Current and Projected Future Climate in the Tropical Americas

Pathogens transmitted by Aedes aegypti mosquitoes, such as the Zika, chikungunya, and dengue viruses, pose a current and potentially expanding threat to human populations in the tropical and sub-tropical Americas. Climate impacts the ecology of the mosquito and pathogens through multiple means. The survival, development, and reproductive behavior of Aedes is largely regulated by temperature and humidity. Precipitation often provides standing water habitats for the immature stages of the mosquito lifecycle. Additionally, the extrinsic incubation period (EIP) of the viruses are often shorter at warmer temperatures. This increases the probability that a mosquito will survive the EIP and become capable of retransmitting the virus to a new human host. Because of the close relationship between Aedes survival and climate, the transmission risk of mosquito-borne pathogens has been mapped and the impact of climate change on their range has been the subject of many prior studies. However, risk varies both geographically and seasonally. Furthermore, rates of change in temperature, humidity, and precipitation are also not uniform spatially or seasonally. We address these issues for dengue by producing monthly maps of current and projected risk of dengue transmission in the tropical and sub-tropical Americas using temperature- and humidity-based mosquito mortality rates and a temperature-based virus incubation period. Risk was assessed under current and projected future climate using NASA’s Earth Exchange Downscaled Climate Projections. The resulting maps indicate that not only is the potential range of transmission increasing, dengue seasonality is also lengthening in many locations. These data will help public health authorities modify the timing and intensity of existing vector control programs, as well as provide important guidance as to where new programs may need to be started in order to protect public health.