Abstract
Recent epidemics of Zika, dengue, and chikungunya have heightened the need to understand the seasonal and geographic range of transmission by Aedes aegypti and Ae. albopictus mosquitoes. We use mechanistic transmission models to derive predictions for how the probability and magnitude of transmission for Zika, chikungunya, and dengue change with mean temperature, and we show that these predictions are well matched by human case data. Across all three viruses, models and human case data both show that transmission occurs between 18–34°C with maximal transmission occurring in a range from 26–29°C. Controlling for population size and two socioeconomic factors, temperature-dependent transmission based on our mechanistic model is an important predictor of human transmission occurrence and incidence. Risk maps indicate that tropical and subtropical regions are suitable for extended seasonal or year-round transmission, but transmission in temperate areas is limited to at most three months per year even if vectors are present. Such brief transmission windows limit the likelihood of major epidemics following disease introduction in temperate zones.
Highlights
Epidemics of dengue, chikungunya, and Zika are sweeping through the Americas, and are part of a global public health crisis that places an estimated 3.9 billion people in 120 countries at risk [1]
We estimated the posterior distribution of R0(T) and used it to calculate key temperature values that indicate suitability for transmission: the mean and 95% credible intervals on the critical thermal minimum, maximum, and optimum temperature for transmission by the two mosquito species
Ae. aegypti transmission peaked at 29.1 ̊C, and declined to zero below 17.8 ̊C and above 34.6 ̊C (Fig 2)
Summary
Chikungunya, and Zika are sweeping through the Americas, and are part of a global public health crisis that places an estimated 3.9 billion people in 120 countries at risk [1]. Chikungunya virus (CHIKV) emerged in the Americas in 2013, causing 1.8 million suspected cases from 44 countries and territories (www.paho.org). In the last two years, Zika virus (ZIKV) has spread throughout the Americas, causing 764,414 suspected and confirmed cases, with many more unreported (http://ais.paho.org/phip/viz/ed_zika_cases.asp, as of April 13, 2017). Predicting transmission of DENV, CHIKV, and ZIKV requires understanding the ecology of the vector species. For these viruses the main vector is Aedes aegypti, a mosquito that prefers and is closely affiliated with humans, while Ae. albopictus, a peri-urban mosquito, is an important secondary vector [4,5]. Mathematical and geostatistical models that incorporate climate information have been valuable for predicting and responding to Aedes spp. spread and DENV, CHIKV, and ZIKV outbreaks [5,6,7,8,9,10]
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