Early-warning surveillance of West Nile and Usutu viruses in wetland and larval habitat waters and in mosquito excreta using digital PCR
6 affiliations
- 1ALTOPICTUS, Pérols, France.
- 2IAGE, Ingénierie et Analyse en Génétique Environnementale, Montpellier, France.
- 3GIS OBEPINE+, Sorbonne Université, Paris, France.
- 4UMR, INSERM, Université de Montpellier, Pathogenesis and Control of Chronic and Emerging Infections, Montpellier, France.
- 5Unité de Parasitologie et Entomologie, Département des Maladies Infectieuses, Institut de Recherche Biomédicale des Armées, Marseille, France.
- 6Aix Marseille Université, IRD, AP-HM, SSA, UMR Vecteurs - Infections Tropicales et Méditerranéennes (VITROME), IHU - Méditerranée Infection, Marseille, France.
Abstract
West Nile virus (WNV) and Usutu virus (USUV) are mainly avian mosquito-borne pathogens, increasingly cause human and equine disease in temperate regions. Mostly asymptomatic, current surveillance in France is reactive, based on clinical and veterinary reports, delaying signals for vector control and preventative interventions. We implemented in Southern France, in 2024 and 2025, a proactive surveillance methodology combining molecular xenomonitoring of mosquito excreta and environmental water detection of viral RNA in wetlands and mosquito larval habitat, through a multiplex reverse transcription digital PCR workflow. The analytics process was characterised through the limits of blank, detection, and quantification. Low-level positives were confirmed by Sanger sequencing. WNV and USUV RNA repeated detections revealed previously unrecognized, cryptic circulations up to 19 weeks before the first WNV human cases and equine alert. Environmental surveillance represents a paradigm shift for early detection of emerging Culex-borne arboviruses and a key enabler of proactive and effective One Health responses. Author summary: West Nile virus (WNV) and Usutu virus (USUV) are mosquito-borne flaviviruses maintained in enzootic cycles involving birds and mosquitoes, with incidental infections in humans and horses. Because most infections are asymptomatic, viral circulation often remains undetected until the onset of clinical cases, limiting the timeliness of current surveillance systems.
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BibTeX
@article{mocq2026earlywarning,
title = {{Early-warning surveillance of West Nile and Usutu viruses in wetland and larval habitat waters and in mosquito excreta using digital PCR}},
author = {Julien Mocq and Julie Raymond and Karine Bolloré and Anaïs Fossot and Rachel Beaubaton and Alexandre Lepeule and Cécile Gruet and Franz Durandet and Jeanne Hanin and Guillaume Lacour and Albin Fontaine and Olivier Courot and Antoine Mignotte and Yannick Simonin},
journal = {PLOS Neglected Tropical Diseases},
year = {2026},
month = oct,
doi = {10.1371/journal.pntd.0014799},
url = {https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0014799},
note = {CC BY},
}
RIS
TY - JOUR
TI - Early-warning surveillance of West Nile and Usutu viruses in wetland and larval habitat waters and in mosquito excreta using digital PCR
AU - Julien Mocq
AU - Julie Raymond
AU - Karine Bolloré
AU - Anaïs Fossot
AU - Rachel Beaubaton
AU - Alexandre Lepeule
AU - Cécile Gruet
AU - Franz Durandet
AU - Jeanne Hanin
AU - Guillaume Lacour
AU - Albin Fontaine
AU - Olivier Courot
AU - Antoine Mignotte
AU - Yannick Simonin
PY - 2026
DA - 2026/10/06
JO - PLOS Neglected Tropical Diseases
DO - 10.1371/journal.pntd.0014799
UR - https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0014799
AB - West Nile virus (WNV) and Usutu virus (USUV) are mainly avian mosquito-borne pathogens, increasingly cause human and equine disease in temperate regions. Mostly asymptomatic, current surveillance in France is reactive, based on clinical and veterinary reports, delaying signals for vector control and preventative interventions. We implemented in Southern France, in 2024 and 2025, a proactive surveillance methodology combining molecular xenomonitoring of mosquito excreta and environmental water detection of viral RNA in wetlands and mosquito larval habitat, through a multiplex reverse transcription digital PCR workflow. The analytics process was characterised through the limits of blank, detection, and quantification. Low-level positives were confirmed by Sanger sequencing. WNV and USUV RNA repeated detections revealed previously unrecognized, cryptic circulations up to 19 weeks before the first WNV human cases and equine alert. Environmental surveillance represents a paradigm shift for early detection of emerging Culex-borne arboviruses and a key enabler of proactive and effective One Health responses. Author summary: West Nile virus (WNV) and Usutu virus (USUV) are mosquito-borne flaviviruses maintained in enzootic cycles involving birds and mosquitoes, with incidental infections in humans and horses. Because most infections are asymptomatic, viral circulation often remains undetected until the onset of clinical cases, limiting the timeliness of current surveillance systems.
SN - 1935-2735
SN - 1935-2727
ER -