Characterising West Nile virus epidemiology in Israel using a transmission suitability index

Abstract

Background Climate 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. Aim We 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. Methods We 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). Results The 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. Conclusions By 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.

West Nile virus in Portugal

“…Figures 4A to 4C). This output showed that, in accordance to previously described geo-temporal patterns for other mosquito-borne viruses [34] and WNV [41] in different countries, natural climate variations strongly influence both inter-and intra-yearly variation in transmission potential. When quantifying the number of months within a year for which the estimated transmission potential was not zero, we again found a clear division between the north and south ( Figures 4BDFH).…”

“…This index is the theoretical transmission potential P of each adult female mosquito in the zoonotic reservoir (derived from the decomposition of R 0 =MP). P can be interpreted as a proxy for the risk of spillover to the human and equine populations (as demonstrated recently for Israel [41]).…”

“…[34,37,39,40]). Recently, the index was also successfully used to estimate the transmission potential of WNV in Israel dependent on local relative humidity and temperature variables [41]. In that study, P was interpreted as a proxy for the risk of spillover to the human population given that it measured the WNV transmission potential by single adult female mosquitoes in the animal reservoir.…”

West Nile virus keeps on moving up in Europe

“…The annual fluctuations in WNV activity can be influenced by several factors. In the current issue of Eurosurveillance, Lourenço et al have analysed West Nile virus epidemiology in Israel [15]. WNV infections caused by diverse strains have been diagnosed in the country in the past decade.…”

West Nile virus detection in horses in three Brazilian states

“…To estimate the transmission potential of WNV we calculated the index P, a computational approach informed by climatic variables from Lourenço et al recently applied in Israel [14] ( see Technical Appendix for detail ). In the 2015-2016 season, cases in Piauí presented a seasonal signal typical of WNV and other mosquito-borne viruses, with a peak between February and May (late summer and autumn).…”