Abstract
Recent epidemics of Zika, dengue, and chikungunya have heightened the need to understand virus transmission ecology for Aedes aegypti and Ae. albopictus mosquitoes. An estimated 3.9 billion people in 120 countries are at risk for these diseases. Temperature defines the fundamental potential for vector-borne disease transmission, yet the potential for transmission in sub-tropical and temperate regions remains uncertain. Using mechanistic transmission models fit to mosquito and virus physiology data and validated with human case data, we show that mean temperature accurately bounds transmission risk for Zika, chikungunya, and dengue in the Americas. Transmission occurs between 18-34°C and peaks at 29°C for Ae. aegypti (between 11-28°C with a peak at 26°C for Ae. albopictus). As predicted, high relative incidence of Zika, dengue, and chikungunya in humans occurs between 23-32°C, peaks at 27-29°C, and is very low outside the predicted range. As a proxy for infrastructure and vector control effort, economic reliance on tourism explains some departures from areas otherwise suitable for high rates of transmission. Nonetheless, the temperature-based models alone provide fundamental eco-physiological measures of transmission potential. Tropical and subtropical regions are suitable for extended seasonal or year-round transmission by Ae. aegypti and Ae. albopictus. By contrast, potential transmission in temperate areas is constrained to at most three months per year even if vectors are present (which is currently not the case for large parts of the US). Such brief transmission windows limit the likelihood and potential extent of epidemics following disease introduction in temperate zones.
Significance statement Viruses transmitted by Aedes aegypti and Ae. albopictus mosquitoes, including Zika, dengue, and chikungunya, present one of the most rapidly growing infectious disease threats, putting an estimated 3.9 billion people in 120 countries at risk. Understanding the relationship between transmission and climate, particularly temperature, is critical for predicting and responding to potential spread into sub-tropical and temperate areas. Using models informed by laboratory experiments and tested against actual human infection data, we show that transmission potential of these three viruses is substantial between 23-32°C and peaks at 27-29°C. This implies that while year-round transmission is likely in tropical and sub-tropical areas, temperate areas are at risk for at most seasonal transmission, given that the necessary mosquito species are present.
