Abstract
BackgroundIn 2015–2016, Zika virus (ZIKV) caused serious epidemics in Brazil. The key epidemiological parameters and spatial heterogeneity of ZIKV epidemics in different states in Brazil remain unclear. Early prediction of the final epidemic (or outbreak) size for ZIKV outbreaks is crucial for public health decision-making and mitigation planning. We investigated the spatial heterogeneity in the epidemiological features of ZIKV across eight different Brazilian states by using simple non-linear growth models.ResultsWe fitted three different models to the weekly reported ZIKV cases in eight different states and obtained an R2 larger than 0.995. The estimated average values of basic reproduction numbers from different states varied from 2.07 to 3.41, with a mean of 2.77. The estimated turning points of the epidemics also varied across different states. The estimation of turning points nevertheless is stable and real-time. The forecast of the final epidemic size (attack rate) is reasonably accurate, shortly after the turning point. The knowledge of the epidemic turning point is crucial for accurate real-time projection of the outbreak.ConclusionsOur simple models fitted the epidemic reasonably well and thus revealed the spatial heterogeneity in the epidemiological features across Brazilian states. The knowledge of the epidemic turning point is crucial for real-time projection of the outbreak size. Our real-time estimation framework is able to yield a reliable prediction of the final epidemic size.
Highlights
In 2015–2016, Zika virus (ZIKV) caused serious epidemics in Brazil
We reveal the spatial heterogeneity of epidemiological parameter estimates of the ZIKV epidemics across Brazil which should be useful in mitigation planning
The Richards model is selected for Acre, Bahia, and Pernambuco; Gompertz model is selected for Mato Grosso and Rio Grande; and the logistic model is selected for Espirito Santo, Goiania City and Parana
Summary
In 2015–2016, Zika virus (ZIKV) caused serious epidemics in Brazil. The key epidemiological parameters and spatial heterogeneity of ZIKV epidemics in different states in Brazil remain unclear. Prediction of the final epidemic (or outbreak) size for ZIKV outbreaks is crucial for public health decision-making and mitigation planning. We investigated the spatial heterogeneity in the epidemiological features of ZIKV across eight different Brazilian states by using simple non-linear growth models. ZIKV is an arbovirus in the family of Flaviviridae and is transmitted through the bites of mosquito vectors (usually of Aedes aegypti mosquitoes) [4,5,6,7]. By 2007, ZIKV had escaped Africa to the Yap island in Micronesia, and it infected an estimated 75% of the local population [8]. Due to the lack of effective vaccines or medication, the World Health Organization (WHO) declared ZIKV as a public health emergency of international concern as of February 2016 [17]
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