3 Jul 20265 min read

France's autochthonous arbovirus surveillance goes weekly, the first two bulletins land

France has become the only EU/EEA country publishing autochthonous arbovirus surveillance at weekly cadence. The first two bulletins of the new system (17 and 24 June 2026) report zero confirmed autochthonous cases, the expected baseline against a 2025 season that delivered 809 chikungunya and 30 dengue cases. The architecture, anchored in 83 *Aedes albopictus*-colonised départements, is the operational benchmark the rest of Europe will be measured against.

Mosticare Editorial
Last updated · 3 Jul 2026
Small fish swimming in green water with white debris.
“Small fish swimming in green water with white debris.” — Photo by Young Kane on Unsplash

France is the only country in the EU/EEA that runs a weekly autonomous autochthonous arbovirus surveillance bulletin at continental granularity, and the system is now operational for the 2026 season. Santé publique France published the second of its new weekly bulletins on 24 June 2026, eight days after the first was published on 17 June. Both bulletins cover the same four pathogens, chikungunya, dengue, Zika and West Nile virus, and both report the same headline number: zero confirmed autochthonous cases in mainland France for the 2026 season to date.

That number is unremarkable in itself. What is remarkable is that the French system is now reporting it every week, in public, on a defined cadence that runs through 30 November 2026.

Why a weekly cadence matters

The reinforced surveillance period for autochthonous arboviruses in metropolitan France runs, by convention, from 1 May to 30 November each year, the window during which Aedes albopictus adult activity, mosquito-borne transmission, and imported-case follow-up can plausibly generate a local cluster. In 2025, that window produced 809 autochthonous chikungunya cases and 30 autochthonous dengue cases across mainland France, the highest chikungunya count since France began systematic autochthonous surveillance in 2006.

The 2025 retrospective, published on 6 May 2026 as the Bilan 2025, is the institutional reference baseline. The chikungunya total comprised 790 cases distributed across 79 transmission clusters (ranging from 1 to 144 cases per cluster) plus 19 isolated cases, with symptom onset dates from 27 May to 13 November 2025. The dengue total comprised 29 cases across 11 transmission clusters (1 to 10 cases per cluster) plus one isolated case, with onset dates from 25 June to 14 September 2025. Transmission clusters occurred in Provence-Alpes-Côte d'Azur, Occitanie, Auvergne-Rhône-Alpes, Corsica and Île-de-France, regions "déjà affectées les années précédentes." For the first time, clusters also appeared in Nouvelle-Aquitaine, Grand Est and Bourgogne-Franche-Comté, a clear sign of the geographic spread of autochthonous transmission risk into regions that were not historically affected. SpF's framing of the 2025 epidemic, "cette épidémie a été causée par une souche virale particulièrement adaptée au moustique Aedes albopictus", captures the strain-adaptive signal that drove last year's severity.

The 2025 season is the reason the 2026 weekly cadence exists. After a year in which the chikungunya total was 26 times the previous high and the geographic footprint widened into three new regions, the operational case for moving from monthly or fortnightly bulletins to a true weekly cadence is straightforward: the early-warning signal for a new autochthonous cluster is most actionable in its first one to two weeks, before secondary transmission establishes a chain.

The new architecture

The two bulletins published so far, 17 June and 24 June 2026, are the first two of the new cadence. The bulletins report case counts and cluster signals from the four-pathogen autochthonous surveillance system, anchored in the départements where Aedes albopictus is established. As of 1 January 2026, Santé publique France's colonisation map counted 83 of France's 96 mainland départements as colonised by Aedes albopictus, the tiger mosquito's geographic footprint now covers the entire Atlantic coast, the Mediterranean, the Rhône valley, the Alpine belt and most of southwestern and central France.

The reinforcement period runs through 30 November 2026. Within that period, the dispositifs de surveillance renforcée in each colonised département operate at heightened tempo: general practitioners and emergency departments are briefed to flag fever-plus-joint-pain or fever-plus-rash presentations with no recent foreign travel, the arbovirus reference laboratory network runs confirmatory PCRs on suspected cases, and the agences régionales de santé (ARS) trigger vector-control responses, larval source reduction, ultra-low-volume adulticide spraying in a 200-metre buffer around suspected cases, door-to-door information campaigns, when an autochthonous case is confirmed.

The framing in the 24 June bulletin captures the architecture in two short phrases: the période renforcée de surveillance des arboviroses runs through 30 November, and the dispositifs de surveillance renforcée are operational in the colonised départements. The bulletins' purpose is to "définir, piloter et coordonner la surveillance épidémiologique", define, lead and coordinate the epidemiological surveillance, across that geography.

What the first two bulletins show

Both bulletins report the same headline number for the 2026 season: zero confirmed autochthonous cases of chikungunya, dengue, Zika and West Nile virus in mainland France as of the surveillance cut-off date (14 June 2026 for the 17 June bulletin; 21 June 2026 for the 24 June bulletin). The full case-count tables are published in the bulletin PDFs.

That zero is, at this point in the season, the expected number. The 2025 autochthonous transmission did not establish itself until late May and early June; the 2026 season, with a slightly cooler spring across the Mediterranean and Atlantic coasts, is following a similar trajectory with a one-to-two-week lag. The first autochthonous cluster of 2026, when it comes, will be reported in the bulletin dated the week after confirmation, which is exactly the operational tempo the new cadence is designed to deliver.

What this changes for residents and travellers

For residents of the colonised départements, and that is most of metropolitan France, including Paris, Lyon, Marseille, Toulouse, Bordeaux, Nantes, Strasbourg and Nice, the weekly bulletin is the new authoritative signal for the autochthonous arbovirus picture in their area. The bulletins are short, public, in French, and updated every Wednesday during the reinforced surveillance period.

For travellers to mainland France between May and November, the bulletins matter in two ways. First, an autochthonous case confirmed in a département triggers an ARS vector-control response within 24 to 48 hours, and the bulletin is the public signal that the response has begun. Second, returning travellers who develop fever-plus-joint-pain or fever-plus-rash within two weeks of a French trip should mention the specific département of stay to their GP; autochthonous chikungunya and dengue are still under-diagnosed in returning-traveller presentations because clinicians do not always include a French département in the differential.

For the wider European vector-borne disease conversation, the French weekly cadence is the operational benchmark. No other EU/EEA country publishes autochthonous arbovirus data at this frequency and this granularity. The French system is what a mature European autochthonous arbovirus surveillance architecture looks like, and it is, for the moment, the only example the rest of the EU/EEA has to learn from.

What to watch over the next twelve weeks

The next twelve bulletins (W26 through W38, covering 24 June through late September) are the season's first autochthonous risk window. The 2025 baseline suggests the first autochthonous chikungunya cluster will appear in late June or early July, with the bulk of transmission running from mid-July through mid-September.

The départements to watch, on the 2025 pattern, are the Var, the Alpes-Maritimes, the Hérault, the Gard, the Bouches-du-Rhône, the Haute-Garonne, the Rhône, the Gironde and, the new addition, the Bas-Rhin and the Haute-Vienne. The first autochthonous cluster outside the historical Mediterranean-Acquitaine belt would be the structurally significant signal of 2026.

What we know

Sources cited

  1. Santé publique France, Bulletin de la surveillance renforcée des arboviroses du 24 juin 2026, second bulletin of the new weekly cadence, published 24 June 2026. https://www.santepubliquefrance.fr/maladies-a-transmission-vectorielle/chikungunya
  2. Santé publique France, Bulletin de la surveillance renforcée des arboviroses du 17 juin 2026, first bulletin of the new weekly cadence, published 17 June 2026. https://www.santepubliquefrance.fr/maladies-a-transmission-vectorielle/chikungunya
  3. Santé publique France, Chikungunya, dengue et Zika en France hexagonale, Bilan 2025, published 6 May 2026. https://www.santepubliquefrance.fr/maladies-a-transmission-vectorielle/chikungunya/bulletin-national/chikungunya-dengue-et-zika-en-france-hexagonale-bilan-2025
  4. Santé publique France, Cartographie de l'implantation du moustique tigre (Aedes albopictus) en France hexagonale, departmental colonisation map, 1 January 2026 cut-off. https://www.santepubliquefrance.fr/maladies-a-transmission-vectorielle/chikungunya