Assessing real-time Zika risk in the United States

Abstract

BackgroundConfirmed local transmission of Zika Virus (ZIKV) in Texas and Florida have heightened the need for early and accurate indicators of self-sustaining transmission in high risk areas across the southern United States. Given ZIKV’s low reporting rates and the geographic variability in suitable conditions, a cluster of reported cases may reflect diverse scenarios, ranging from independent introductions to a self-sustaining local epidemic.MethodsWe present a quantitative framework for real-time ZIKV risk assessment that captures uncertainty in case reporting, importations, and vector-human transmission dynamics.ResultsWe assessed county-level risk throughout Texas, as of summer 2016, and found that importation risk was concentrated in large metropolitan regions, while sustained ZIKV transmission risk is concentrated in the southeastern counties including the Houston metropolitan region and the Texas-Mexico border (where the sole autochthonous cases have occurred in 2016). We found that counties most likely to detect cases are not necessarily the most likely to experience epidemics, and used our framework to identify triggers to signal the start of an epidemic based on a policymakers propensity for risk.ConclusionsThis framework can inform the strategic timing and spatial allocation of public health resources to combat ZIKV throughout the US, and highlights the need to develop methods to obtain reliable estimates of key epidemiological parameters.Electronic supplementary materialThe online version of this article (doi:10.1186/s12879-017-2394-9) contains supplementary material, which is available to authorized users.

Repurposing of the anti-malaria drug chloroquine for Zika Virus treatment and prophylaxis

“…ZIKV is a member of the Flaviviridae family of viruses, which are transmitted to humans by mosquitoes and ticks and are responsible for millions of infections annually. ZIKV has historically been restricted to tropical/sub-tropical regions but it has now reached the Southern USA 2 . Recent studies have demonstrated that ZIKV infects and predominantly damage human neural precursors; however, the cellular and molecular mechanisms of ZIKV pathogenesis remain poorly understood 3 – 6 .…”

Quantifying the risk of local Zika virus transmission in the contiguous US during the 2015–2016 ZIKV epidemic

“…Concerns have been raised that several other locations in the contiguous US were at risk of ZIKV transmission, thus triggering a number of studies aimed at identifying populations at highest risk of local transmission [ 10 – 20 ]. In particular, detailed studies based on environmental suitability, epidemiological factors, and travel-related case importations have been used to estimate the risk for specific counties in the US [ 21 , 22 ]. In this study, we quantify the risk of local ZIKV transmission by using a data-driven stochastic and spatial epidemic model accounting for seasonal, environmental, and detailed population data.…”

Modelling microbial infection to address global health challenges

“…Models may be used to infer R 0 as well as forecast changes in R 0 that could drive transitions in epidemic dynamics, such as the shift from sporadic outbreaks to sustained chains of transmission. Example: assessing real-time Zika risk in Texas 90 .…”

“…In contrast to univariate sensitivity analyses, uncertainty analysis simultaneously samples from empirical-or expert-informed distributions for many or all input parameters. Collaboration between modellers and disease experts is thus instrumental to ensuring the biological plausibility of these parameter distributions 90,91 . The uncertainty analysis produces both a central point estimate and a range for each outcome, a combination which can inform stakeholders about the best-case and worst-case scenarios as well as the likelihood that an intervention will be successful [92][93][94] .…”