Genomic Epidemiology of West Nile Virus in Paris

What are the spatial and temporal dynamics of West Nile virus (WNV) circulation in France, and what is the virus lineage at the origin of the 2025 emergence in the Paris area?In this study, conducted between 2022 and 2025 and integrating human, veterinary, and entomological surveillance across France, only lineage 2 was detected among the 52 WNV-positive samples analyzed. The phylogenetic analysis linked Mediterranean virus strains to those circulating in the South Atlantic over previous years and found that the 2025 Paris outbreak was caused by virus strains also originating from the South Atlantic sublineage.These findings suggest WNV expansion in France is sustained by both local maintenance and long-distance dispersal across regions, underscoring the need for strengthened genomic surveillance to anticipate future emergence.

Corresponding Author: Albin Fontaine, PhD, Unité des Virus Emergents, 19-21 Bd Jean Moulin, 13005 Marseille, France (albin.fontaine@univ-amu.fr).

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