Abstract
BackgroundClimate is a major factor in the epidemiology of West Nile virus (WNV), a pathogen increasingly pervasive worldwide. Cases increased during 2018 in Israel, the United States and Europe.AimWe set to retrospectively understand the spatial and temporal determinants of WNV transmission in Israel, as a case study for the possible effects of climate on virus spread.MethodsWe employed a suitability index to WNV, parameterising it with prior knowledge pertaining to a bird reservoir and Culex species, using local time series of temperature and humidity as inputs. The predicted suitability index was compared with confirmed WNV cases in Israel (2016–2018).ResultsThe suitability index was highly associated with WNV cases in Israel, with correlation coefficients of 0.91 (p value = 4 × 10− 5), 0.68 (p = 0.016) and 0.9 (p = 2 × 10− 4) in 2016, 2017 and 2018, respectively. The fluctuations in the number of WNV cases between the years were explained by higher area under the index curve. A new WNV seasonal mode was identified in the south-east of Israel, along the Great Rift Valley, characterised by two yearly peaks (spring and autumn), distinct from the already known single summer peak in the rest of Israel.ConclusionsBy producing a detailed geotemporal estimate of transmission potential and its determinants in Israel, our study promotes a better understanding of WNV epidemiology and has the potential to inform future public health responses. The proposed approach further provides opportunities for retrospective and prospective mechanistic modelling of WNV epidemiology and its associated climatic drivers.
Highlights
Global trends that favour the establishment of mosquitoes and movement of infectious hosts are promoting the geographical expansion and epidemic activity of mosquito-borne viruses [1,2,3,4]
West Nile virus (WNV) endemicity is maintained in a transmission cycle between mosquitoes and birds, with human and equine spillover outbreaks caused by the broad host tropism of the mosquito species involved (Culex spp.)
In this study we explored the application of a mosquito-borne virus suitability measure, the index P, to characterise the recent spatio-temporal epidemiology of WNV in Israel
Summary
Global trends that favour the establishment of mosquitoes and movement of infectious hosts (humans and animals) are promoting the geographical expansion and epidemic activity of mosquito-borne viruses [1,2,3,4] Important examples of these trends are the recent Zika virus epidemic, which had severe public health consequences in Central and South America [5,6,7,8], the yellow fever vaccination crisis in African countries [9] and (re)emergence of yellow fever virus in Brazil [9,10]. Most human infections are believed to escape passive surveillance systems owing to their mild clinical nature, a small proportion of people may develop encephalitis with a substantial risk of death Because of the latter, WNV is considered one of the most important agents of viral encephalitis globally [15,16]. The proposed approach further provides opportunities for retrospective and prospective mechanistic modelling of WNV epidemiology and its associated climatic drivers
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