Eurosurveillance - Volume 31, Issue 16, 23 April 2026

While West Nile virus (WNV), a mosquito-borne zoonotic pathogen, is detected every year in animals in Spain, clinical human cases occur more sporadically. Most explanatory and predictive models for WNV circulation focus on single components and aggregate multiple year data into a single dataset.

We sought WNV circulation environmental drivers across different ecological components (vectors, reservoirs, and dead-end hosts), by analysing their spatial and temporal dynamics.

We used active and passive surveillance data collected in Spain between 2003 and 2022, encompassing mosquitoes, 120 bird species, 115 mammal species, and humans. To understand WNV circulation, mosquito spatial and host spatiotemporal models were developed, incorporating current and lagged environmental variables. Our One Health approach integrated the different models to determine WNV exposure risk, including 1 year in advance.

Over 20 years, WNV exposure risk in Spain rose by 19% in birds, 17% in non-human mammals, and 38% in humans. In birds and non-human mammals, exposure more likely occurred in areas experiencing mean respective annual temperatures > 5 °C and > 8 °C in the previous year. In humans, increased exposure risk concurred with mild winters (> 5.3 °C). Integrating mosquito and host models found the country’s southern half and mediterranean coast most suited for WNV. Predictive models solely using prior-year variables yielded comparable results to contemporaneous ones.

The models suggest that annual human WNV transmission may occur more regularly than evidenced by surveillance, possibly due to asymptomatic or misdiagnosed cases. Our framework could serve as an early warning tool, enhancing outbreak preparedness up to 1 year ahead.

West Nile virus (WNV) has become established across Europe, with Hungary serving as a key transmission hub since 2004. Following reduced activity during 2020–22, the 2024 season marked a resurgence with the largest geographical distribution ever recorded in Europe.

To analyse the 2024 WNV transmission season in Hungary using a One Health approach and characterise circulating strains within the European phylogeographic context using comprehensive genomic surveillance.

Complete and near-complete genome sequencing was performed on 55 specimens from 38 humans, 15 birds and two Culex pipiens mosquito pools using amplicon-based next-generation sequencing. Phylogeographic analysis incorporated 637 European WNV genome sequences (2004–24) with time-scaled Bayesian phylogenetic reconstruction and continuous spatial diffusion modelling.

Hungary reported 113 human WNV cases in 2024 (n = 111 autochthonous, 2 imported), a 3.7-fold increase from 2023 (incidence: 1.16 vs 0.31 per 100,000 population). Neuroinvasive disease predominated (92%, n = 104) with a 7.9% case fatality rate. All 55 sequenced strains belonged to WNV lineage 2. Phylogeographic analysis revealed Hungary's central role in European WNV dissemination since 2004, with multiple introductions and local diversification across distinct clades. Continuous spatial modelling identified Hungary as a persistent transmission hub with bidirectional viral flow to neighbouring countries, contributing to northward expansion.

Hungary remains a critical WNV transmission hub in Central Europe with established endemicity of multiple lineage 2 clades. The analysis highlights Hungary's role as both a recipient and major source of European WNV diversity, emphasising the need for coordinated surveillance and climate-adapted preparedness strategies.