Dengue without international travel, three 2026 papers map Europe's autochthonous pattern

France recorded 809 autochthonous chikungunya cases and 30 autochthonous dengue cases across mainland France in 2025. The chikungunya total is the highest recorded in France since enhanced surveillance began in 2006. The dengue total is small by comparison, but it landed inside an institutional year in which autochthonous arbovirus transmission stopped being an outlier across the temperate Mediterranean.

Three papers published in 2026, by researchers in Spain, Italy and the United Kingdom, with co-authors across both, have now built the institutional frame for what is happening. Taken together, the three papers say something none of them would say alone: autochthonous dengue in Europe is not a 2025 anomaly. It is the structural shape of what comes next.

What the institutional papers actually say

The first paper, by Fernando Agüero and colleagues at the Hospital Universitari General de Catalunya, the University of Ferrara, the University of Milan-Bicocca and the IRCCS Istituto Auxologico Italiano, was published in The Journal of Travel Medicine on 25 June 2026. Its title is direct: "Dengue without international travel: Europe at the interface of seasonality, vectors, and preparedness." The framing is the public-health-preparedness side, what European surveillance and clinical-detection systems need to do when the index case has not left the country.

The second paper, by Giulia Campinopoli, Antonino Di Caro, Giuseppe Ippolito and a multinational team including authors from University College London, was published in Biology Direct on 12 June 2026 under the title "Autochthonous dengue transmission in Europe: epidemiology, mechanisms, and modelling insights." It is a structured review, free to read, and its abstract is the clearest single institutional statement on the shift to date. "Recent outbreaks in Italy, Spain, and France," the authors write, "together with evidence of under-recognised transmission, indicate a transition from sporadic importation to recurrent autochthonous infection." The drivers, Aedes albopictus establishment, climatic suitability, increased case importation, and delays in clinical recognition, are stated in their most tightly linked form. The paper's most-quoted line is also its most cautious: "The emergence of dengue in Europe should be viewed as an early signal of broader changes in vector-borne disease dynamics."

The third paper, by Pasquale Stefanizzi and colleagues from Apulia Region and other Italian public-health institutions, was published in Frontiers in Public Health on 8 May 2026. It is technically a chikungunya paper, but functions inside the dengue conversation as the Italian policy-level view: where the gaps in surveillance and preparedness sit, what vector-control and risk-communication tools are unevenly implemented, and what targeted vaccination could add.

What 2025's continental picture looked like

The French 2025 surveillance bilan, published by Santé publique France on 6 May 2026, is the single densest autochthonous-arbovirus dataset published for any European country in the year. The headline totals: 809 autochthonous chikungunya cases, the highest since enhanced surveillance began in 2006, and 30 autochthonous dengue cases, both acquired inside mainland France with no international travel history. The chikungunya signal clustered around the documented 2025 outbreaks; the dengue signal was smaller but geographically scattered.

A separate 2025 Italian data point, published by Dora Buonfrate and colleagues from the IRCCS Sacro Cuore Don Calabria in Verona and collaborators in The Journal of Infectious Diseases in May 2026, ran a structured arbovirus-screening protocol in Verona province across the summer of 2025. Of 102 people presenting with acute fever and no recent travel history, 29-28.4 percent, turned out to have an autochthonous arboviral infection: 22 chikungunya, 4 tick-borne encephalitis, 3 West Nile fever. The Verona study is the cleanest 2025 datapoint on how easily autochthonous arbovirus infection goes undetected in the routine clinical pathway.

A decade-scale Spanish data anchor fills out the picture. Cristina Báguena and colleagues, in Enfermedades Infecciosas y Microbiología Clínica (English edition) in May 2026, run a ten-year retrospective, 2014 to 2024, of dengue and chikungunya in the Region of Murcia, the Iberian Mediterranean coastal belt where Ae. albopictus has been established for years. Autochthonous transmission in Mediterranean Spain is a decade-long pattern at low background levels, with episodic spikes when conditions align.

The four drivers, and what the papers say about each

Across the three 2026 institutional papers, the four drivers of Europe's autochthonous dengue shift are the same four, and the framing of each is now slightly more concrete than it was a year ago.

Vector expansion is the structural precondition: in the absence of an established Ae. albopictus population, autochthonous transmission is biologically impossible. The Campinopoli review maps the European distribution as contiguous from the Iberian Mediterranean coast through southern France into the Italian peninsula, with established populations also reported across the Balkans and the Pannonian basin.

Climate sits upstream. The Stefanizzi paper frames climate change as the pressure; the Campinopoli paper places "increasing climatic suitability" in the same sentence as vector expansion. The Ae. albopictus northern and altitudinal range has expanded in lockstep with warmer winters, longer warm seasons, and shorter cold-snap intervals across most of temperate Europe.

Case importation is the trigger. The Agüero paper treats this as the side of the equation where every autochthonous case begins with an imported one. Mainland France imported roughly 500 dengue cases in the first five months of 2026 alone, a number large enough that the probability of a returning traveller landing in an Ae. albopictus receptive area during the warm season, and being bitten within the infectious viraemic window, is now structurally elevated.

Clinical detection is the close-out. The Verona paper makes this concrete: 28.4 percent of unexplained acute-fever presentations in a single Veneto province turned out to be autochthonous arbovirus. The gap between the true autochthonous caseload and the reported autochthonous caseload is large, and that gap closes only when clinical suspicion rises.

What the papers mean for prevention

The three papers converge on a single set of prevention recommendations. Integrated surveillance, both entomological and epidemiological, is the base layer. Diagnostic capacity for dengue and chikungunya needs to be available at the front-line clinical level, not centralised in reference laboratories, so the Verona 28.4 percent figure can be matched across other receptive provinces. Vector control needs to move from reactive to anticipatory, with explicit targeting of Ae. albopictus urban-temperate habitats, domestic garden containers, urban green-space water features, peri-urban tyre and cistern sites. The Stefanizzi paper adds the policy-prevention layer: integrated risk communication, transparent publication of local transmission data, and targeted vaccination where appropriate. Vaccines and novel vector-control tools, including Wolbachia-based interventions, are flagged as complementary rather than primary; the main weight sits on surveillance, clinical detection, and conventional vector control.

What to watch across the rest of 2026

The 2026 Ae. albopictus season opened early in the Mediterranean basin. France's reinforced arbovirus surveillance, running 1 May to 30 November 2026, is now in its eighth week. Spain's Mediterranean coastal surveillance is operating with the Murcia 2014-2024 baseline as its reference frame. Italy's national integrated surveillance is operating with the Verona and Apulia 2025 experience as its most-recent institutional memory. The first autochthonous dengue or chikungunya case of 2026 anywhere on the Mediterranean basin will be the season's trigger event.

For travellers and residents in the European Ae. albopictus belt, coastal Spain, southern France, the Italian peninsula from Lombardy southward, the Adriatic coast, the Pannonian basin, the operative advice is unchanged: cover up at dawn and dusk, use a proven repellent on exposed skin, empty standing water weekly from balconies and gardens, and sleep under treated netting or in screened rooms. For unexplained acute fever in a receptive area during the warm season, ask the clinician to add dengue and chikungunya to the differential, the Verona 28.4 percent figure is the institutional reason why.

What we know

• France recorded 809 autochthonous chikungunya cases and 30 autochthonous dengue cases across mainland France in 2025, the highest chikungunya total since enhanced surveillance began in 2006. Santé publique France, Bilan 2025, published 6 May 2026
• Three 2026 institutional papers, Agüero (J Travel Med, 25 Jun 2026), Campinopoli (Biol Direct, 12 Jun 2026), and Stefanizzi (Front Public Health, 8 May 2026), frame the European autochthonous dengue signal as a structural shift, not a 2025 outlier. Agüero F et al., PMID 42348729; Campinopoli G et al., PMID 42286757; Stefanizzi P et al., PMID 42180454
• In Verona province, Italy, 28.4 percent (29 of 102) of unexplained acute-fever presentations during summer 2025 turned out to be locally acquired arboviral infection, 22 chikungunya, 4 tick-borne encephalitis, 3 West Nile fever. Buonfrate D et al., J Infect 2026;92(5):106730 (PMID 41845966)
• A 10-year retrospective (2014-2024) of dengue and chikungunya in the Region of Murcia, Spain, documents the decade-scale autochthonous background signal across the Iberian Mediterranean coast. Báguena C et al., Enferm Infecc Microbiol Clin (Engl Ed) 2026;44(5):503159 (PMID 41967310)
• Four drivers appear consistently across the 2026 institutional literature: Aedes albopictus expansion, climate-driven suitability, increased case importation from endemic regions, and delays in clinical detection. Campinopoli G et al., PMID 42286757

Sources cited

1. Agüero F, Antonazzo IC, Paccini M, Rozza D, Mantovani LG, Ferrara P. Dengue without international travel: Europe at the interface of seasonality, vectors, and preparedness. J Travel Med 2026;taag048. DOI: 10.1093/jtm/taag048. PMID 42348729. https://pubmed.ncbi.nlm.nih.gov/42348729/
2. Campinopoli G, Di Caro A, D'Alise A, Conventi F, McHugh TD, Melino G, Zumla A, Ippolito G. Autochthonous dengue transmission in Europe: epidemiology, mechanisms, and modelling insights. Biol Direct 2026;21(1). DOI: 10.1186/s13062-026-00868-3. PMID 42286757. https://pubmed.ncbi.nlm.nih.gov/42286757/
3. Stefanizzi P, Lopalco P, Balena V, Vitale V, Iannelli G, Martinelli D, Termite S, Centrone F, Chironna M, Fortunato F. Chikungunya virus infection in Italy: epidemiology, climate change implications and public health recommendations. Front Public Health 2026;14:1791544. DOI: 10.3389/fpubh.2026.1791544. PMID 42180454. https://pubmed.ncbi.nlm.nih.gov/42180454/
4. Buonfrate D, Ancillotti L, Zanchi C, Mazzi C, Cattaneo P, Mori A, Accordini S, Cheri S, Waggoner JJ, Castilletti C, Gobbi F. High burden of autochthonous arboviral infections during the summer season in Verona province, Italy, during 2025. J Infect 2026;92(5):106730. DOI: 10.1016/j.jinf.2026.106730. PMID 41845966. https://pubmed.ncbi.nlm.nih.gov/41845966/
5. Báguena C, Chirlaque López MD, Martínez Portillo A, et al. A decade of mosquito-borne arboviral infections in the Region of Murcia: Clinical and epidemiological description of dengue and chikungunya (2014-2024). Enferm Infecc Microbiol Clin (Engl Ed) 2026;44(5):503159. PMID 41967310. https://pubmed.ncbi.nlm.nih.gov/41967310/
6. Santé publique France, Bilan annuel 2025, Surveillance des arboviroses en France hexagonale, published 6 May 2026. https://www.santepubliquefrance.fr/
7. European Centre for Disease Prevention and Control, Surveillance Atlas of Infectious Diseases: Dengue virus infection. https://www.ecdc.europa.eu/en/dengue/surveillance-and-disease-data