Molina Grane C and colleagues at Fondazione Bruno Kessler and the Istituto Superiore di Sanita, working with the Toscana Centro and Emilia-Romagna public-health departments, published "Autochthonous transmission patterns of dengue virus serotype 2 in Italy: evidence from outbreaks in 2024" in Eurosurveillance in July 2026 (PMID 42428999). The reconstruction analyses 296 locally acquired DENV-2 cases with symptom onset from 31 July to 31 October 2024 across four Italian regions, the largest number of autochthonous dengue cases ever recorded in mainland Europe. Using a Bayesian framework to reconstruct transmission chains between well-documented exposure sites, the authors estimate the generation time and the net reproduction number, moving the Italian dengue picture from imported-case risk to a quantified account of sustained local transmission on Aedes albopictus. The study is the upstream surveillance anchor for the consumer-protection layer at the human-vector interface across the Mediterranean basin.
A consortium led by Fondazione Bruno Kessler and the Istituto Superiore di Sanità, working with the Prevention Department Public Health Unit Toscana Centro in Florence and the Emilia-Romagna Region Collective Prevention and Public Health Department in Bologna, published a peer-reviewed reconstruction of Italy's 2024 autochthonous dengue outbreaks in Eurosurveillance, the ECDC-hosted European communicable-disease bulletin, in July 2026. In 2024, multiple dengue virus serotype 2 (DENV-2) transmission foci were detected across four Italian regions, producing the largest number of autochthonous dengue cases ever recorded in mainland Europe. The authors analysed 296 locally acquired cases with symptom onset from 31 July to 31 October 2024, reconstructed the transmission chains between well-documented exposure sites using a Bayesian framework, and estimated the generation time and the net reproduction number for the outbreaks. The study is the first peer-reviewed quantitative characterisation of the 2024 Italian DENV-2 events as the largest mainland-European autochthonous dengue episode on record, and it supplies the upstream surveillance anchor for the consumer-protection layer at the human-vector interface across the Mediterranean basin.
What Molina Grané et al. actually measured
The reconstruction rests on three linked analytical steps. First, the authors assembled the 296 locally acquired DENV-2 cases with symptom onset from 31 July to 31 October 2024 across the four affected regions, a case series with sufficient documentation of where and when each person was likely exposed. Second, they used a Bayesian framework to reconstruct the transmission chains that connected the well-documented exposure sites, inferring which cases were plausibly linked to which earlier cases given the timing and the geography. Third, from those reconstructed chains they estimated two quantitative epidemiological parameters: the generation time, which measures the average interval between one case and the cases it gives rise to, and the net reproduction number, which measures how many secondary cases each case produced as the outbreaks unfolded.
The headline count is the structural signal. Two hundred and ninety-six locally acquired cases in a single season is the largest number of autochthonous dengue cases ever recorded in mainland Europe, and the fact that the foci were distributed across four regions rather than confined to a single town marks a shift in scale from the isolated clusters of earlier European seasons. The symptom-onset window from late July to the end of October maps onto the seasonal activity period of the vector, Aedes albopictus, the tiger mosquito that is now established across much of the Italian peninsula.
The transmission-chain reconstruction is what makes the paper a primary milestone rather than a case count. By linking cases to exposure sites in a Bayesian framework, the authors move beyond the observation that local transmission occurred to a quantified account of how it propagated. The generation-time and net-reproduction-number estimates give surveillance authorities and modellers a common set of parameters against which to compare the 2024 Italian outbreaks with autochthonous dengue events elsewhere in Europe and with the imported-case baseline. This is the kind of quantitative surveillance evidence that anchors an editorial frame rather than a headline that decays after a news cycle.
Why the autochthonous-dengue peg matters for the 2026 cycle
The Molina Grané reconstruction matters for three reasons. First, it formalises the transition in the Italian dengue picture from imported-case risk to documented sustained local transmission. Second, it pairs with the wider 2026 European vector-surveillance surface to complete an Italy and France Western-Mediterranean autochthonous and imported dengue platform. Third, it locates the consumer-protection layer precisely where the transmission actually happens, at the exposure-site clusters that the transmission-chain reconstruction identifies.
The first point is the most important for the editorial frame. For most of the past two decades the European dengue narrative was an imported-case narrative: travellers returned from endemic regions with dengue, and the concern was whether a local Aedes albopictus population would pick the virus up and start a local chain. The EpiCentro arbovirosi dashboard Q2 close update, posted 9 July 2026, still records the imported baseline clearly, with Italy reporting 169 imported dengue cases, 13 imported chikungunya cases, and 3 imported Zika cases in the first half of 2026, all imported. The Molina Grané paper documents what happens when the imported baseline meets an established and abundant vector in a favourable season: 296 locally acquired cases across four regions. The 2024 outbreaks are the proof of concept for sustained autochthonous transmission in mainland Europe, and the peer-reviewed reconstruction is the durable citation for it.
The second point is the most important for the platform. The Italian DENV-2 reconstruction sits alongside the Santé publique France reinforced-surveillance bulletins, which record continuing imported dengue pressure in metropolitan France, and alongside the autochthonous-dengue framing established by Ippolito and Zumla in Lancet Regional Health Europe. Together these sources describe a Western-Mediterranean corridor in which imported introductions and an established vector combine to produce local transmission of increasing scale. The ECDC invasive-mosquito distribution map, which records Aedes albopictus established in 16 European countries and 369 regions and Aedes aegypti newly recorded in Luxembourg, is the geographic backbone that explains why the corridor is widening.
The third point is the most important for the consumer-protection layer. The transmission-chain reconstruction identifies the exposure sites where transmission concentrated. Autochthonous dengue does not spread from person to person directly; it spreads because an infected person is bitten by a local mosquito that then bites others in the same area. That places the intervention window squarely at the human-vector interface, in the gardens, courtyards, container habitats, and outdoor living spaces where the tiger mosquito breeds and bites. Source reduction to remove standing water, physical barriers to keep mosquitoes away from people, and personal repellent use are the measures that operate at exactly the point in the transmission chain that the Bayesian reconstruction highlights.
What the Molina Grané peg does NOT say
The reconstruction is precise about what it establishes, and the editorial frame should be equally precise about what it does not. The paper characterises the 2024 outbreaks; it is not a forecast of the 2026 season, and it does not claim that 2026 will match or exceed the 2024 count. The 2024 event was the largest on record in mainland Europe, but the reconstruction is a retrospective analysis, not a prediction. The paper documents DENV-2 transmission specifically; it does not address chikungunya, Zika, or West Nile virus, each of which follows its own vector and transmission dynamics. The paper is a surveillance and modelling study; it does not evaluate any specific consumer-protection product, repellent formulation, or barrier method, and it makes no claim about the comparative effectiveness of any intervention. The consumer-protection relevance is a downstream application of the transmission-chain finding, not a result reported in the study. Finally, the paper is not a statement about medical countermeasures. It documents where and how local transmission occurred; it does not evaluate vaccines or antivirals, and nothing in the reconstruction should be read as a comment on the countermeasure pipeline. The frame is autochthonous-transmission surveillance and the in-season consumer-protection layer, not a judgement on any upstream medical intervention.
What to watch next
The 2026 W28 editorial platform should track four near-term developments. First, any 2026-season Italian autochthonous dengue or West Nile virus update, whether from the EpiCentro arbovirosi and WNV bulletins or from regional public-health authorities, would test whether the 2024 pattern reconstructed by Molina Grané et al. is recurring in the current season. Second, the Santé publique France reinforced arboviroses bulletin, published weekly through the transmission season, will record the metropolitan France imported-dengue trajectory and any autochthonous transmission, the western half of the Western-Mediterranean corridor. Third, the ECDC invasive-mosquito distribution map and the ECDC monthly worldwide dengue overview will track whether Aedes albopictus continues to expand across the 369 recorded regions and whether the Aedes aegypti introduction in Luxembourg represents establishment or a single detection. Fourth, the consumer-protection editorial frame should follow these institutional surfaces and pair each surveillance update with practical guidance for households, travellers, and outdoor workers in the exposure-site settings that the transmission-chain reconstruction identifies as the concentration points for local transmission.
The consumer-protection layer for the 2026 Mediterranean dengue season is the in-season complement to the quantitative surveillance evidence reported by Molina Grané et al. The Bayesian transmission-chain reconstruction explains where and how autochthonous DENV-2 propagated across four Italian regions in 2024; the consumer-protection layer operates at the human-vector interface, at the exposure sites and container habitats where the transmission actually occurred, independent of imported-case pressure and independent of any specific medical countermeasure. The two are complementary rather than substitutable, and the W25 platform message that the physical barrier is the layer available now, for everyone, with no supply ceiling and no excluded cohort, is the durable consumer-protection framing that pairs with the Eurosurveillance reconstruction without supplanting it. The institutional recognition that mainland Europe has now recorded its largest autochthonous dengue event is the upstream signal; the consumer-protection layer is the in-season complement that operates at the household, traveller, and outdoor-worker level across the Mediterranean basin as Aedes albopictus continues to establish across the 16 European countries and 369 regions mapped by the ECDC invasive-mosquito surveillance atlas.
Published 2026-07-11 · Mosticare Editorial