Introduction and Spread of West Nile Virus in Lazio, Italy, 2025: Molecular Epidemiology and Genomic Characterization
8 affiliations
- 1National Institute for Infectious Diseases "Lazzaro Spallanzani" IRCCS, Rome, Italy.
- 2Centre for Epidemic Response and Innovation (CERI), School of Data Science and Computational Thinking, Stellenbosch University, Stellenbosch, South Africa.
- 3Emerging Pathogens Institute, Department of Pathology, College of Medicine, University of Florida, Gainesville, Florida, USA.
- 4Istituto Zooprofilattico Sperimentale del Lazio e della Toscana "M. Aleandri", Rome, Italy.
- 5Genetics and Genomics Institute, University of Florida, Gainesville, Florida, USA.
- 6Department of Experimental Medicine, University of Rome "Tor Vergata", Rome, Italy.
- 7Department of Infectious Diseases, Istituto Superiore di Sanità, Rome, Italy.
- 8Area Promozione della Salute e Prevenzione, Direzione Regionale Salute e Integrazione Sociosanitaria, Rome, Regione Lazio, Italy.
Abstract
West Nile virus (WNV) is a flavivirus whose cycle involves mosquitoes and avian hosts that occasionally may infect horses and humans as "dead-end hosts." Human infection is mostly asymptomatic, sometimes leading to febrile or neuroinvasive disease. In 2025, Italy experienced its largest epidemic with an unprecedented geographic spread (79 provinces; 52% of cases in central Italy). Here we report whole‑genome sequencing and phylogeographic analysis of 39 WNV lineage 2 samples collected in Lazio and Campania regions between July and September 2025 from humans and animal samples. All 2025 strains belonged to a Southern Italian clade that diversified around 2020, with evidence of earlier circulation in 2024. All the 2025 genomes shared a substitution that lies in envelope protein domain III (K399R), potentially influencing interactions with the viral membrane. The same mutation was previously detected in Eastern European strains, leading to the hypothesis of introductions in Italy via migratory birds from these regions. Phylogeography identified strong viral dispersal routes within Central Italy supporting a pattern of short‑range spread and local overwintering. Overall, results highlight the roles of ecological conditions and cross‑border transmission dynamics in shaping the 2025 Italian epidemic, underscoring the need for integrated genomic/ecological surveillance.
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BibTeX
@article{rueca2026introduction,
title = {{Introduction and Spread of West Nile Virus in Lazio, Italy, 2025: Molecular Epidemiology and Genomic Characterization}},
author = {Martina Rueca and Cesare Ernesto Maria Gruber and Gabriella De Carli and Ilaria Mussetto and Carla Nartuhi Mavian and Giuseppe Manna and Francesca Rosone and Davide La Rocca and Juan Guillermo Perez-Jimenez and Maria Teresa Scicluna and Giovanni Chillemi and Eliana Specchiarello and Francesca Colavita and Flavia Smoquina and Alessandra Nappo and Christina Merakou and Marcello Giovanni Sala and Claudio De Liberato and Giulietta Venturi and Andrea Siddu and Francesco Vairo and Fabrizio Maggi and Fabrizio Carletti},
journal = {Journal of medical virology},
year = {2026},
month = oct,
doi = {10.1002/jmv.71188},
url = {https://europepmc.org/article/PMC/PMC13717939},
note = {CC BY-NC-ND},
}
RIS
TY - JOUR
TI - Introduction and Spread of West Nile Virus in Lazio, Italy, 2025: Molecular Epidemiology and Genomic Characterization
AU - Martina Rueca
AU - Cesare Ernesto Maria Gruber
AU - Gabriella De Carli
AU - Ilaria Mussetto
AU - Carla Nartuhi Mavian
AU - Giuseppe Manna
AU - Francesca Rosone
AU - Davide La Rocca
AU - Juan Guillermo Perez-Jimenez
AU - Maria Teresa Scicluna
AU - Giovanni Chillemi
AU - Eliana Specchiarello
AU - Francesca Colavita
AU - Flavia Smoquina
AU - Alessandra Nappo
AU - Christina Merakou
AU - Marcello Giovanni Sala
AU - Claudio De Liberato
AU - Giulietta Venturi
AU - Andrea Siddu
AU - Francesco Vairo
AU - Fabrizio Maggi
AU - Fabrizio Carletti
PY - 2026
DA - 2026/10/29
JO - Journal of medical virology
DO - 10.1002/jmv.71188
UR - https://europepmc.org/article/PMC/PMC13717939
AB - West Nile virus (WNV) is a flavivirus whose cycle involves mosquitoes and avian hosts that occasionally may infect horses and humans as "dead-end hosts." Human infection is mostly asymptomatic, sometimes leading to febrile or neuroinvasive disease. In 2025, Italy experienced its largest epidemic with an unprecedented geographic spread (79 provinces; 52% of cases in central Italy). Here we report whole‑genome sequencing and phylogeographic analysis of 39 WNV lineage 2 samples collected in Lazio and Campania regions between July and September 2025 from humans and animal samples. All 2025 strains belonged to a Southern Italian clade that diversified around 2020, with evidence of earlier circulation in 2024. All the 2025 genomes shared a substitution that lies in envelope protein domain III (K399R), potentially influencing interactions with the viral membrane. The same mutation was previously detected in Eastern European strains, leading to the hypothesis of introductions in Italy via migratory birds from these regions. Phylogeography identified strong viral dispersal routes within Central Italy supporting a pattern of short‑range spread and local overwintering. Overall, results highlight the roles of ecological conditions and cross‑border transmission dynamics in shaping the 2025 Italian epidemic, underscoring the need for integrated genomic/ecological surveillance.
SN - 0146-6615
SN - 1096-9071
ER -