Detection of West Nile virus via retrospective mosquito arbovirus surveillance, United Kingdom, 2025

Abstract

In March 2025, as part of ongoing enhanced surveillance for mosquito-borne Orthoflaviviruses, West Nile virus (WNV) RNA was detected in two pools of female Aedes vexans collected in July 2023 in Nottinghamshire, England. Sequencing and phylogenetic analysis of a 402 bp fragment indicate clustering with WNV lineage 1a. The exact origin of this virus remains unclear, but this finding indicates a historic WNV presence in the United Kingdom. Surveillance has not provided evidence of further WNV transmission to date.