Concern is mounting that the recent emergence, resurgence, and spread of vector-borne and zoonotic diseases such as dengue, chikungunya, Zika, and malaria, is connected to climate change. Mosquito-transmitted diseases are intimately linked with environmental temperature and humidity because of mosquito and pathogen physiological responses, including growth, development, survival, reproduction, and behavior. Current models often inaccurately predict that warmer temperatures will tend to increase mosquito transmission even as temperatures warm above 30°C. In contrast, models that include more physiologically accurate, nonlinear thermal responses of the mosquito and pathogen vital rates that drive transmission predict intermediate optimal temperatures (e.g., 25°C for falciparum malaria). Here, we develop a model of arbovirus transmission (particularly dengue, chikungunya, and Zika viruses) by Aedes aegypti and Ae. albopictus mosquitoes that includes physiologically accurate, nonlinear mosquito and parasite thermal responses.
Results/Conclusions
Ae. aegypti and Ae. albopictus development rates, longevity, fecundity, and biting rates have hump-shaped responses to temperature with intermediate optima. Whether viral extrinsic incubation rate is hump-shaped or increases linearly remains unclear. As a result, dengue, chikungunya, and Zika virus transmission are optimal at intermediate temperatures (25-29°C), consistent with field data on the number of human dengue and chikungunya cases across space and time. These intermediate optimal temperatures are robust to uncertainty in trait thermal responses. Together, the results imply that while warming temperatures may increase disease transmission at higher latitudes and altitudes, they are not likely to increase transmission in the most heavily affected tropical and sub-tropical regions.