3 Jul 20266 min read

Two countries. Three cases. Three areas. The European WNV surveillance platform just held its line through Q2 close, and a global host-prevalence dataset now offers the structural foundation for the second half of summer 2026

Two countries. Three cases. Three areas. ECDC's W25 and W26 West Nile virus weekly bulletins both report the same tallies, Italy Caserta, Italy Firenze, North Macedonia Vardarski, and the European surveillance platform has now held that line through Q2 close (30 June 2026). On 26 June 2026 a global host-prevalence and competence dataset (Richter-Boix et al., Scientific Data, PMID 42362577) was published, converting the clinical case counts into the transmission-cycle structure. Combined with Hungary's 2024 hub (Nagy 2026), the late-May heatwave excess-mortality bulletin published by Santé publique France on 30 June 2026, and the Riccetti, Patzina-Mehling and Heidecke papers on land cover, urban amplification and thermal R0, the second half of summer 2026 has its institutional foundation laid.

Mosticare Editorial
Last updated · 3 Jul 2026
Rippling blue water surface with light reflections
“Water - Wasser” — Photo by Esther Heidsiek-Schmitten on Unsplash

Two countries. Three cases. Three areas. ECDC's two most recent West Nile virus weekly bulletins, W25 (data to 17 June 2026) and W26 (data to 24 June 2026), report the same continental tally. Italy carries two human cases, in the province of Caserta (Campania) and the metropolitan area of Firenze (Toscana). North Macedonia carries one human case, in the Vardar region. There are no deaths, no new countries and no new areas. The W27 bulletin is not yet published; ECDC's working-day cadence points to Friday 3 July 2026. The carry-forward hold through Q2 close (30 June 2026) is the cleanest institutional stability frame of the 2026 European vector season.

What "no change for two weeks" actually means

The ECDC West Nile virus weekly is the reference dashboard for European vector-borne disease during the transmission season, pulling confirmed human case reports from EpiPulse and from national authorities. The W25 and W26 bulletins sit seven calendar days apart. The continental totals have not moved.

ECDC's on-the-record line across both weeks is consistent: "seasonal weather conditions are currently favourable for mosquito-borne transmission; therefore more cases are expected to occur in the coming weeks." It does not predict where the next case will land, but it does confirm that the Culex pipiens-driven European WNV cycle is, in mid-2026, running inside its expected climate envelope. With Q2 close behind us and the W27 bulletin pending, the European WNV surveillance platform has held its opening line through the half-year boundary.

The Richter-Boix dataset: clinical counts become transmission-cycle structure

The new research layer that converts these clinical counts into transmission-cycle structure was published on 26 June 2026 in Scientific Data. Richter-Boix and colleagues have assembled a global database of West Nile virus host prevalence and competence, a curated, harmonised resource that puts bird hosts, mosquito vector species and mammalian dead-end hosts onto a single comparative grid for the first time in 2026. The dataset is the structural foundation under the European clinical case counts: it tells institutional readers not just that two countries have reported three cases, but how those cases sit inside a wider cycle of ornithophilic mosquito vectors, amplifying bird hosts and serologically positive mammals across Europe, Africa and the Americas.

The Richter-Boix paper is the eighth in a 2026 series that has progressively replaced the clinical-without-ecology picture of European WNV with a transmission-with-ecology picture. The prior seven include the Nagy 2026 Euro Surveill Hungary hub study, the Riccetti 2026 iScience land-cover analysis, the Patzina-Mehling 2026 Nature Communications Berlin urban-amplification study, the Heidecke 2026 One Health thermal-R0 analysis, the Klitting 2026 JAMA Network Open Paris genomic study, the Heinrich 2026 endemic-progression paper and the Antonov 2026 lineage-2 analysis. The Richter-Boix paper is the layer that binds them together.

Hungary 2024: the persistent hub the global dataset now maps

The continental position behind the European WNV line is set by Hungary. The Nagy team's April 2026 Eurosurveillance paper sequenced 55 strains from the 2024 Hungarian season and combined them with 637 European WNV genomes from 2004 to 2024. Hungary reported 113 human cases in 2024-111 autochthonous, 92 percent neuroinvasive, 7.9 percent fatal, every sequenced strain lineage 2. Phylogeographic modelling identified two persistent viral corridors running outward from Hungary: westward along the Danube into central Europe, and southeastward into the Balkans via Serbia, Romania and the North Macedonian Vardar region.

The North Macedonian case now sitting on the ECDC W25/W26 table is, in genomic terms, downstream of the Hungarian hub along that second corridor. The Italian cases in Caserta and Firenze sit on the Mediterranean flyway rather than the Danubian one, but the Italian integrated surveillance system's early, broad opening is consistent with what the land-cover and thermal-R0 layers predict. The Richter-Boix dataset maps that picture globally; the Nagy paper maps the European hub; the W25/W26 bulletins map this season's clinical output.

The climate-amplification signal: SpF canicule 24-28 May 2026

The piece of the picture that the clinical bulletins do not show is the climate layer. On 30 June 2026, Santé publique France published a national bulletin on excess mortality during the 24-28 May 2026 heatwave episode: Canicule et santé : excès de mortalité durant l'épisode de canicule du 24 au 28 mai 2026. The five-day heatwave ran ahead of the meteorological start of summer, and its excess-mortality signal is the structural reason the ECDC "more cases expected" line sits where it does.

Pair the SpF bulletin with the Heidecke thermal-R0 analysis and the Patzina-Mehling Berlin urban-amplification paper, and the climate layer reads as the structural substrate for the second half of summer 2026, not a prediction of case numbers, but an explanation of why the surveillance platform's stability triangle is a leading indicator rather than a lagging one. The Swiss Culex pipiens ecotype work from Perrin and colleagues completes the picture: competence varies by ecotype, latitude and season, which is why the same European climate envelope can produce different clinical outcomes in different regions.

What to watch across the rest of summer 2026

The next four ECDC WNV bulletins, W27 (data to 1 July, expected Friday 3 July 2026), W28, W29 and W30, 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. The W25/W26 stability frame tells us the season opened small and held; the Richter-Boix dataset, the Nagy hub paper and the climate-amplification signal tell us the structural substrate for wider European transmission is now in place.

For individual readers across the WNV belt, Italy, the Balkans, the Hungarian basin, the warmer river-valley corridors of central Europe, the long-standing personal-protection advice has not changed: 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, gardens and roof gutters, 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

Sources cited

  1. Richter-Boix A, et al. A global database of West Nile virus host prevalence and competence. Sci Data. 2026 Jun 26. PMID: 42362577. https://pubmed.ncbi.nlm.nih.gov/42362577/
  2. 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/
  3. 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
  4. 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
  5. Santé publique France. Canicule et santé : excès de mortalité durant l'épisode de canicule du 24 au 28 mai 2026, national bulletin, published 30 June 2026. https://www.santepubliquefrance.fr/les-actualites
  6. Nagy A, Erdélyi K, Molnár Z, et al. Hungary as a source of West Nile virus diversity and spread in Europe: insights from the 2024 transmission season. Euro Surveill. 2026;31(16):2500785. PMID: 42141881; PMCID: PMC13109698. https://pubmed.ncbi.nlm.nih.gov/42141881/
  7. Perrin Y, et al. Culex pipiens ecotypes and vector competence in Switzerland. Parasit Vectors. 2026. PMID: 42363267. https://pubmed.ncbi.nlm.nih.gov/42363267/
  8. 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/
  9. Patzina-Mehling C, et al. Urban amplification of West Nile virus transmission in Berlin. Nat Commun. 2026. PMID: 42285951. https://pubmed.ncbi.nlm.nih.gov/42285951/
  10. Heidecke J, et al. Thermal R0 of West Nile virus in European vectors. One Health. 2026. PMID: 42294014. https://pubmed.ncbi.nlm.nih.gov/42294014/
  11. Klitting R, et al. Genomic epidemiology of West Nile virus in Paris. JAMA Netw Open. 2026.
  12. Heinrich N, et al. Endemic progression of West Nile virus in Europe. Eur J Microbiol Immunol. 2026.
  13. Antonov V, et al. Lineage 2 dynamics of West Nile virus in Europe. Virology. 2026.
    Published 2026-07-01 · Mosticare Editorial