Hungary as a source of West Nile virus diversity and spread in Europe: insights from the 2024 transmission season

BACKGROUNDWest 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.AIMTo 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.METHODSComplete 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.RESULTSHungary 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.CONCLUSIONHungary 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.