Global risk model for vector-borne transmission of Zika virus reveals the role of El Niño 2015

Abstract

Zika, a mosquito-borne viral disease that emerged in South America in 2015, was declared a Public Health Emergency of International Concern by the WHO in February of 2016. We developed a climate-driven R0 mathematical model for the transmission risk of Zika virus (ZIKV) that explicitly includes two key mosquito vector species: Aedes aegypti and Aedes albopictus. The model was parameterized and calibrated using the most up to date information from the available literature. It was then driven by observed gridded temperature and rainfall datasets for the period 1950–2015. We find that the transmission risk in South America in 2015 was the highest since 1950. This maximum is related to favoring temperature conditions that caused the simulated biting rates to be largest and mosquito mortality rates and extrinsic incubation periods to be smallest in 2015. This event followed the suspected introduction of ZIKV in Brazil in 2013. The ZIKV outbreak in Latin America has very likely been fueled by the 2015–2016 El Niño climate phenomenon affecting the region. The highest transmission risk globally is in South America and tropical countries where Ae. aegypti is abundant. Transmission risk is strongly seasonal in temperate regions where Ae. albopictus is present, with significant risk of ZIKV transmission in the southeastern states of the United States, in southern China, and to a lesser extent, over southern Europe during the boreal summer season.

Establishment and cryptic transmission of Zika virus in Brazil and the Americas

“…1b, c; adjusted R 2 > 0.84, P < 0.001; Extended Data Table 1b). Similar to previous findings from dengue virus outbreaks 14,15 , notified ZIKV cases lag climatic suitability by about 4–6 weeks in all regions, except northeast Brazil, where no time lag is evident. Despite these associations, numbers of notified cases should be interpreted cautiously because co-circulating dengue and chikungunya viruses exhibit symptoms similar to ZIKV, and the Brazilian case reporting system has evolved through time (see Methods).…”

Could the Recent Zika Epidemic Have Been Predicted?

“…As it has been shown by other authors (Turner et al, 2013; Caminade et al, 2017) the equations for the dynamics of a two-vector one-host SIR model, a generalization of the standard Ross-McDonald model (Smith et al, 2012), are $\begin{array}{c}eqnarrayright\; center\; left\frac{d{S}_H}{dt}=-{\lambda }_H{S}_H\end{array}$ $\begin{array}{c}eqnarrayright\; center\; left\frac{d{I}_H}{dt}={\lambda }_H{S}_H-r{I}_H\end{array}$ $\begin{array}{c}eqnarrayright\; center\; left\frac{d{R}_H}{dt}=r{I}_H\end{array}$ $\begin{array}{c}eqnarrayright\; center\; left\frac{d{S}_i}{dt}={\rho }_i{N}_i-{\lambda }_{Vi}{S}_i-{\mu }_i{S}_i\end{array}$ $\begin{array}{c}eqnarrayright\; center\; left\frac{d{L}_i}{dt}={\lambda }_{Vi}{S}_i-false({\nu }_i+{\mu }_{i}false)L_i\end{array}$ $\begin{array}{c}eqnarrayright\; center\; left\frac{d{I}_i}{dt}={\nu }_i{L}_i-{\mu }_i{I}_i\end{array}$ where S H , I H , and R H are the number of susceptible, infectious and recovered hosts, respectively, associated with the Aedes -borne disease of interest. S i , L i , and I i are the number of susceptible, latent and infectious vectors of kind i = 1,2 ( Ae.…”

Evaluating Vaccination Strategies for Zika Virus in the Americas

“…The appropriate vaccine strategy to deploy under any improvements in vector control, such as more aggressive efforts or the introduction of genetically-modified Wolbachia (42,43), can be determined by considering the lower attack rate scenarios in our sensitivity analyses. Likewise, long-term shifts in mosquito prevalence, as might be driven by climate change, could be represented by varying the attack rates (44,45). …”