Europe's 2026 West Nile virus season has opened, and held steady for two weeks running
Europe's 2026 West Nile virus season opened early and has now held still for two consecutive ECDC weeks. The W25 (data to 17 June) and W26 (data to 24 June) bulletins both report two countries, three cases and three affected areas, Italy in Caserta and Firenze, North Macedonia in Vardar, with no deaths. The structural question for July and August is whether the early, broad opening the land-cover and climate models predict will widen from this stable base.
Europe's 2026 West Nile virus season has opened, and is, so far, holding remarkably still. The European Centre for Disease Prevention and Control's weekly bulletin produced on 26 June 2026, with data as of 24 June, reports exactly the same tally as the previous week's bulletin: two countries, three cases, three affected areas. Italy carries two cases, in the provinces of Caserta (Campania) and Firenze (Toscana). North Macedonia carries one case, in the Vardar region. There are no deaths. There are no new countries. There are no new areas.
That, in three numbers, is the continental story of week 26.
What "no change" actually means
The ECDC WNV weekly is the European vector-borne disease community's reference dashboard during the transmission season. Refreshed every Thursday during the European transmission season, it pulls confirmed human case reports from EpiPulse, the EU's epidemic intelligence platform, and from national authorities. The W25 bulletin (data to 17 June) and the W26 bulletin (data to 24 June) sit seven calendar days apart. The totals have not moved. ECDC's W26 weekly states the position in the fewest possible words: "two countries in Europe reported three human cases."
This is unusual, but not unprecedented. The 2025 Italian season finished at 779 cases and 72 deaths across nine regions, a case-fatality ratio of 9.2 percent and the season's heaviest signal in the central Mediterranean. The 2026 season opened roughly six to eight weeks earlier than 2025's peak, depending on which region you measure from, and the early cases clustered in two geographically separate Italian provinces, Caserta on the Campanian coast about 40 kilometres north of Naples, and Firenze in the Florence metropolitan area, rather than in the historical WNV belt of the Po Valley, Calabria and Puglia. That dispersion is the structural signal, not the absolute number: two unrelated Italian areas confirming autochthonous cases in the same week is consistent with the Italian integrated surveillance system's prediction of an early, broad opening.
The North Macedonian case, in the Vardar region, is a non-EU/EEA datapoint that has been on the ECDC table since week 24. It is the only case reported outside Italy in the 2026 continental tally so far.
The ECDC framing for the season ahead
The W26 Communicable Disease Threats Report, published 26 June 2026 and covering the period 19 to 26 June, treats West Nile virus as one of its lead items alongside Ebola, Crimean-Congo haemorrhagic fever, influenza A(H9N2), cholera, mpox, dengue, travel-associated chikungunya and the EU/EEA respiratory virus overview. The CDTR's framing is the continental outlook rather than the weekly case count, and the framing is consistent with what the institutional literature has been saying for two years: European WNV transmission is no longer a late-summer, southern-Mediterranean event. It is opening earlier, in a wider geography, in line with climate-driven shifts in the Culex pipiens vector's range and activity.
What the 2026 land-cover paper says
The peer-reviewed anchor for the framing is a 15 April 2026 paper in iScience by Riccetti and colleagues at the European Commission's Joint Research Centre and an international team. The paper analyses West Nile virus disease incidence across European provinces (NUTS3 level) from 2005 to 2019, using spatial regression models to disentangle the role of land cover, climate, and socio-demographic variables.
The headline finding: shrubland cover is the strongest and most spatially consistent positive predictor of human WNV incidence; forest cover is generally negative; urban and cropland cover have weaker, regionally variable effects. Climatic factors, particularly warm summer temperatures and seasonal moisture balance, are dominant predictors. Socio-economic variables (population density, GDP per capita) contribute little at this scale.
The Riccetti paper is the third in a 2026 series of European WNV urban-temperate and land-cover studies; the prior work includes Klitting and colleagues on the genomic side, Heinrich on vector competence, Patzina-Mehling on seroprevalence in northern Germany, Heidecke on the German veterinary surveillance system, and Antonov on modelling. The convergent finding across the six papers is that Culex pipiens, the common European house mosquito, is establishing stable WNV transmission in regions that were not historically WNV-active, and that the geography of risk is set by climate and land cover together, with shrubland as the most consistent signal.
What the 2026 European map looks like so far
The 2026 mainland European WNV signal has, to date, landed in Campania and Tuscany, not in the historical Mediterranean basin stronghold of Calabria, Puglia, Greece, Romania, Hungary or Serbia. This is a smaller geography than 2025, and a much smaller geography than 2024 (which saw significant transmission in Austria, Hungary, Serbia and Romania). Whether the 2026 season stays small or widens in July and August depends on three variables: summer temperature and moisture balance across the central Mediterranean, the size of the late-spring Culex pipiens adult population across the Po Valley and the Balkans, and the migratory-bird arrival pattern through June and July.
ECDC's W26 CDTR includes the framing that the warm-season weather conditions are currently favourable for mosquito-borne transmission across most of southern and central Europe, which is the institutional signal that the season's first stress test begins in early July.
What to watch across the next four weeks
The next three ECDC bulletins, W27 (data to 1 July, expected Monday 29 June or Friday 3 July 2026), W28 (data to 8 July), and W29 (data to 15 July), are the season's first real expansion test. The 2025 baseline points to Greece, Romania, Hungary, Serbia and Spain as the most likely next countries to report. If the season's trajectory matches last year's, the Italian total will be in the low double digits by the end of July and in the hundreds by mid-September.
For individual readers in Italy, and, from the start of July, across the historical WNV belt, the operative advice has not changed in a decade: cover up at dusk and dawn when Culex pipiens is most active, use a proven repellent on exposed skin, empty standing water weekly from balconies and gardens, and sleep under treated netting or in screened rooms in rural and peri-urban areas. The 200-metre buffer around a confirmed case is the public-instrument response; the personal perimeter is the immediately-actionable layer.
What we know
- Two countries, three cases, three areas. ECDC's W25 weekly (data to 17 June) and W26 weekly (data to 24 June) both report identical totals: Italy (2 cases, Caserta province, Campania; metropolitan Firenze, Toscana) and North Macedonia (1 case, Vardar region). ECDC WNV weekly, produced 26 June 2026
- No deaths reported; no new countries; no new areas. ECDC W26 CDTR, published 26 June 2026
- The 2026 Italian cases opened the season six to eight weeks earlier than 2025's peak, in two geographically separate areas, not in the historical WNV belt of the Po Valley, Calabria and Puglia. ECDC WNV weekly; EpiCentro ISS arbovirosi portal
- Across Europe, shrubland cover is the strongest land-cover predictor of human WNV incidence, with warm summer temperatures and seasonal moisture balance as the dominant climatic predictors, per a 2026 pan-European NUTS3 analysis of 2005-2019 data. Riccetti N et al., iScience 2026;29(6):115754 (PMID 42317728)
- The 2025 Italian season finished at 779 cases, 72 deaths, CFR 9.2 percent across 9 regions, the most recent baseline for the 2026 trajectory. EpiCentro ISS arbovirosi portal
Sources cited
- European Centre for Disease Prevention and Control, West Nile virus infection weekly bulletin, data as of 24 June 2026, produced 26 June 2026. https://wnv-weekly.ecdc.europa.eu/
- European Centre for Disease Prevention and Control, Communicable Disease Threats Report, 19-26 June 2026, Week 26, published 26 June 2026. https://www.ecdc.europa.eu/en/publications-data/communicable-disease-threats-report-19-26-june-2026-week-26
- European Centre for Disease Prevention and Control, Surveillance Atlas of Infectious Diseases: West Nile virus infection, current season (2026). https://www.ecdc.europa.eu/en/west-nile-virus-infection/surveillance-and-disease-data
- Riccetti N, Cescatti A, Ciscar JC, Dubois G, Fanelli A, Figuerola J, Ibarreta D, Szewczyk W, Massaro E. Spatial role of land cover on West Nile virus disease in Europe. iScience 2026;29(6):115754. DOI: 10.1016/j.isci.2026.115754. PMID 42317728; PMCID PMC13273564. https://pubmed.ncbi.nlm.nih.gov/42317728/
- EpiCentro (Istituto Superiore di Sanità), Arbovirosi in Italia: sorveglianza integrata nazionale, Piano Nazionale Arbovirosi 2026. https://www.epicentro.iss.it/arbovirosi/