ANRS MIE & DZIF Joint symposium at ESCMID Global 2026

ANRS MIE & DZIF Joint Symposium

On the occasion of ESCMID Global 2026, ANRS MIE and the German Center for Infection Research (DZIF) are organizing a symposium dedicated to the future of West Nile virus (WNV) research in Europe.

The Scientific organisation includes Marylyn ADDO, University Medical Center Hamburg-Eppendorf (UKE), German Center for Infection Research (DZIF), Germany; Eric D’ORTENZIO, ANRS Emerging infectious diseases, France; Anna PAPA-KONIDARI, Aristotle university school of medicine, Greece.

Objectives

The symposium brings together experts in virology, entomology, ecology and climate research, clinical research and public health, with the overall aim of establishing a joint research agenda capable of supporting earlier detection, strengthening our understanding of the mechanisms involved, and improving epidemic preparedness in Europe.

Topics to be addressed include the development of aligned research strategies and comparative studies on vector-borne diseases.

The programme

The programme consists of four sessions:

• Arboviruses in Europe: framing West Nile virus within an evolving epidemiological and preparedness landscape. Marion KOOPMANS, Erasmus MC, the Netherlands
• Paris under threat: a One Health investigation of the 2025 West Nile virus emergence. Laura PEZZI, National Reference Centre (NRC) for Arboviruses, France
• Emergence and establishment of WNV in Germany. Christian DROSTEN, Institute of Virology, Charite Universitätsmedizin, Germany
• Clinical aspects and management of neuroinvasive West Nile virus infection. Luisa BARZON, EU Reference Laboratory for Public Health on Vector-borne Viruses, Italy

Paris under threat: a One Health investigation of the 2025 West Nile virus emergence

Laura Pezzi is a researcher at the National Reference Centre (CNR) for Arboviruses in Marseilles. Her research focuses on the diagnosis, detection and characterisation of viruses in humans and mosquitoes.

In July 2025, the West Nile virus (WNV) emerged in Paris and northern France, with the first human cases ever recorded. The Île-de-France episode affected two patients with no history or risk factors, both of whom developed a neurological form of the disease.

Using samples collected as part of surveillance of humans, animals and mosquitoes between 2022 and 2025, Laura Pezzi and her team traced the spatial and temporal dynamics of the virus’s circulation in France, thereby characterising the lineage responsible for this emergence and identifying the most likely source of importation.
Only lineage 2 was detected. Phylogenetic analysis linked Mediterranean viral strains to those that had circulated in the Nouvelle-Aquitaine region (South Atlantic) in previous years. It also revealed that the 2025 outbreak in Paris was caused by viral strains also originating from the ‘South Atlantic region’ sublineage.

Historically, West Nile virus has been reported in the eastern Mediterranean region, comprising most of the Provence-Alpes-Côte d’Azur region and Corsica (1), and in the western Mediterranean region, including the coast of Occitanie (2), connected by the Camargue wetland, which overlaps with both regions. The most recent detections have occured in the South Atlantic area, specifically coastal Nouvelle-Aquitaine (3) and, in 2025, in the Paris region (4).

West Nile virus presence in France in 2025 (enomic epidemiology of West Nile virus in Paris. Klitting R, et al. JAMA Network Open. 2026;9(2):e2559588)

According to Laura Pezzi, given that WNV circulation in Europe is driven by several distinct mechanisms that cannot be determined on the basis of virus occurence data alone, genomic data are essential for establishing a link between viral strains circulating across regions.

She supports the ‘One Health’ approach, which relies on assessing virus spread by using samples from various components of the transmission chain (human, equine avian, and mosquitoe hosts). Cross-sectoral data integration, shared alert thresholds, and coordinated outbreak investigations are essential for better studying emerging zoonoses in Europe and responding to them effectively.

Clinical aspects and management of neuroinvasive West Nile virus infection

Luisa Barzon is affiliated with the EU Reference Laboratory for Public Health on Vector-Borne Viruses in Italy. Her clinical and research activities focus primarily on the epidemiology, genetics, pathogenesis and diagnosis of emerging pathogens, in vitro modelling of diseases, innate and adaptive immune responses to viral infections and vaccines, and the application of new biotechnologies in diagnostic microbiology.

West Nile virus (WNV) is transmitted by mosquito vectors between wild and domestic birds, which act as amplifying/reservoir hosts. Humans and equines are incidentally infected through Culex mosquitoe bite and may develop serious neurological disease; however, they are dead-end hosts, as the low level of viraemia cannot sustain onward transmission.

Infection in humans is generally asymptomatic. Fewer than 1% of patients develop neurological complications (meningitis, encephalitis, flaccid paralysis), with a mortality rate of between 10 and 20% among serious cases.

Luisa Barzon told us that in Italy, the regions reporting most human cases of infection were Veneto, Lombardy, Emilia-Romagna, Piedmont and Sardinia.

She presented the results of entomological, veterinary and human surveillance carried out in Veneto in 2022 and 2023 for WNV and the Ussuri virus (USUV), an RNA virus belonging, like WNV, to the genus Orthoflavivirus. Virological and/or serological analyses showed high viral circulation in the region during these two years. In 2022, early viral circulation was associated with earlier infection in wild birds and precocious occurence of a high number of human and equine WNV cases. This year, the endemic WNV lineage 2 was circulating alongside lineage 1, which had recently arrived in the region. Resident birds had a higher positivity rate than migratory birds. In 2023, the results were the reverse.

In 2023, viral circulation was lower than in 2022, as were infection rates in mosquitoes and birds and the number of human cases. There is currently no curative treatment for humans. In cases of neuroinvasive forms, patients receive supportive care, involving hospitalisation, respiratory support and close monitoring of vital signs.

In Europe, a drier winter, high spring temperatures and summer drought are associated with earlier and more widespread circulation of WNV in vectors, birds and humans.

For Luisa Barzon, the results obtained in Veneto support the efficacy of the ‘One Health’ approach for WNV surveillance. In this approach, human medicine, entomology and veterinary disciplines are interconnected and mutually functional.