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• Carla Molina Grané¹ , Martina Del Manso² , Mattia Manica¹ , Chiara Sacco² , Francesco Menegale¹ , Antonino Bella² , Flavia Riccardo³ , Augusto Liverani⁴ , Alessia Pesaresi⁴ , Giovanna Mattei⁵ , Giulio Matteo⁵ , Adriano Murgano⁶ , Dalia Palmieri⁶ , Barbara Rita Porchia⁷ , Chiara Staderini⁸ , Dengue risk assessment working group⁹ , Patrizio Pezzotti^2,* , Stefano Merler^1,* , Piero Poletti^1,*

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  Affiliations:

  ¹ Center for Health Emergencies, Fondazione Bruno Kessler, Trento, Italy

  ² Department of Infectious Diseases, Istituto Superiore di Sanità, Rome, Italy

  ³ External Relations Office and Centre for International Affairs, Istituto Superiore di Sanità, Rome, Italy

  ⁴ Pesaro Urbino Local Health Unit, Pesaro and Urbino, Pesaro, Italy

  ⁵ Emilia-Romagna Region Collective Prevention and Public Health Department, Bologna, Italy

  ⁶ Prevention, Food Safety and Veterinary Service, Abruzzo Region Health Department, Italy

  ⁷ Prevention, workplace safety and public health of Toscana Region, Italy

  ⁸ Prevention department, Public Health Unit, Toscana Centro, Florence, Italy

  ⁹ The members of this group are listed under Collaborators

  * These authors contributed equally to the work and share last authorship.

  Correspondence: 

  Piero Poletti

  poletti fbk.eu

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  Dengue risk assessment working group: Tiziana Lazzarotto, Alessandra Fantuzzi, Giacomo Creola, Ada Mammarella, Matteo Consorte, Claudio Turchi, Flavio Valerio, Vincenzo Cordella, Sara Brugnoli, Giulia Di Pisa, Fabio Filippetti, Lolita Sebastianelli, Irene Mercuri, Francesca Diotallevi

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  Citation style for this article: Molina Grané Carla, Del Manso Martina, Manica Mattia, Sacco Chiara, Menegale Francesco, Bella Antonino, Riccardo Flavia, Liverani Augusto, Pesaresi Alessia, Mattei Giovanna, Matteo Giulio, Murgano Adriano, Palmieri Dalia, Porchia Barbara Rita, Staderini Chiara, Dengue risk assessment working group, Pezzotti Patrizio, Merler Stefano, Poletti Piero. Autochthonous transmission patterns of dengue virus serotype 2 in Italy: evidence from outbreaks in 2024. Euro Surveill. 2026;31(27):pii=2600035. https://doi.org/10.2807/1560-7917.ES.2026.31.27.2600035 Received: 12 Jan 2026;   Accepted: 01 Apr 2026

BACKGROUND

In 2024, multiple transmission foci of dengue virus serotype 2 (DENV-2) were detected across four Italian regions, resulting in the largest number of autochthonous cases ever recorded in mainland Europe.

AIM

We aimed to characterise DENV-2 transmission patterns in Italy in 2024.

METHODS

We analysed 296 locally acquired cases with symptom onset between 31 July and 31 October. Using detailed spatiotemporal data, we reconstructed transmission chains between cases with well-documented exposure sites, applying a Bayesian framework. We estimated the generation time and net reproduction number (Rt) for the main transmission foci, quantified the proportion of transmission occurred across varying distances and assessed the influence of different factors, including temperature and control interventions, on secondary transmission.

RESULTS

Three major foci were identified, with peak Rt estimates ranging from 1.35 to 3.33. The mean generation time was 18.0 days (95% credible interval (CrI): 15.5–20.0 days). Household transmission accounted for 15.4% (95% CrI: 12.6–17.4%) of infection events. Among cases with an identified source of infection, < 1% of transmissions occurred beyond 400 m. Transmissibility declined significantly after outbreak detection, with the average number of secondary cases per infection dropping from 1.4 to 0.4. Vector control interventions were associated with a 41.0% reduction (95% CI: 6.6–63.3%) in transmission; transmission also increased by 19.8% (95% CI: 11.3–29.0%) for each 1°C rise in temperature.

CONCLUSION

Autochthonous dengue outbreaks in Italy in 2024 were primarily driven by short-distance transmission. Our findings support that early case detection and rapid vector control are instrumental in reducing transmission.