Autochthonous chikungunya virus outbreak in Verona province, Italy, 2025
Abstract
Background: Chikungunya virus (CHIKV), primarily transmitted by Aedes mosquitoes, has increasingly caused autochthonous outbreaks in temperate regions, including Italy. In 2025, a local CHIKV outbreak occurred in Verona province, Veneto Region. We report the findings of integrated epidemiological, virological and entomological investigations.
Methods: In 2025, a dedicated surveillance protocol was implemented to assess local transmission of arboviral infections in Verona province, enabling early detection of a local CHIKV circulation. Following notification of the index case, investigations were conducted in accordance with the national and regional arbovirus surveillance plans, including comprehensive epidemiological, virological and entomological analyses.
Results: The index case was identified on 6 August 2025, with retrospective detection of the first case with symptom onset on 31 July; the primary case was not identified. As of 15 October, 69 cases were reported (62 confirmed, 7 probable), with a mean age of 55 years; 91.3% had identifiable epidemiological links, mainly clustered in two municipalities of the Verona province. Most cases (76.8%) occurred between mid-August and mid-September. The outbreak lasted approximately 15 weeks, from the end of July to the mid of October. CHIKV-RNA was detectable in whole blood and, less frequently, urine only within the first 5 days after symptom onset, with higher viral loads in blood. CHIKV-specific IgM antibodies were detectable from Days 4–5 and IgG from Days 7–10. A total of 225 Aedes albopictus specimens were collected, all testing negative for CHIKV. Phylogenetic analysis revealed a highly homogeneous, monophyletic cluster within the East-Central-South African genotype, closely related to strains from the 2024–2025 Réunion outbreak.
Conclusions: This outbreak underscores the value of dedicated surveillance protocols for early detection of febrile/suspected arboviral cases, while also highlighting key vulnerabilities, namely, an undetected primary case and negative entomological findings, pointing to the need for lower testing thresholds and earlier, risk-based vector sampling.
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BibTeX
@article{castilletti2026autochthonous,
title = {{Autochthonous chikungunya virus outbreak in Verona province, Italy, 2025}},
author = {Concetta Castilletti and Leonardo Ancillotti and Antonio Mori and Silvia Accordini and Michela Deiana and Samuele Cheri and Natasha Gianesini and Lorena Maria Chesini and Simone Malagò and Andrea Matucci and Federico Cubi and Chiara Zanchi and Paolo Cattaneo and Ralph Huits and Luisa Barzon and Monia Pacenti and Davide Gentili and Michele Tonon and Chiara Postiglione and Francesco Marchiori and Salvatore Falcone and Tamara Zerman and Federica Gobbo and Christina Merakou and Martina Del Manso and Fabrizio Montarsi and Giulietta Venturi and Patrizio Pezzotti and Dora Buonfrate and Giovanna Varischi and Anna Teresa Palamara and Francesca Russo and Federico Giovanni Gobbi},
journal = {Journal of Travel Medicine},
year = {2026},
month = aug,
doi = {10.1093/jtm/taag079},
url = {https://doi.org/10.1093/jtm/taag079},
note = {CC BY-NC 4.0},
}
RIS
TY - JOUR
TI - Autochthonous chikungunya virus outbreak in Verona province, Italy, 2025
AU - Concetta Castilletti
AU - Leonardo Ancillotti
AU - Antonio Mori
AU - Silvia Accordini
AU - Michela Deiana
AU - Samuele Cheri
AU - Natasha Gianesini
AU - Lorena Maria Chesini
AU - Simone Malagò
AU - Andrea Matucci
AU - Federico Cubi
AU - Chiara Zanchi
AU - Paolo Cattaneo
AU - Ralph Huits
AU - Luisa Barzon
AU - Monia Pacenti
AU - Davide Gentili
AU - Michele Tonon
AU - Chiara Postiglione
AU - Francesco Marchiori
AU - Salvatore Falcone
AU - Tamara Zerman
AU - Federica Gobbo
AU - Christina Merakou
AU - Martina Del Manso
AU - Fabrizio Montarsi
AU - Giulietta Venturi
AU - Patrizio Pezzotti
AU - Dora Buonfrate
AU - Giovanna Varischi
AU - Anna Teresa Palamara
AU - Francesca Russo
AU - Federico Giovanni Gobbi
PY - 2026
DA - 2026/08/29
JO - Journal of Travel Medicine
DO - 10.1093/jtm/taag079
UR - https://doi.org/10.1093/jtm/taag079
AB - Background: Chikungunya virus (CHIKV), primarily transmitted by Aedes mosquitoes, has increasingly caused autochthonous outbreaks in temperate regions, including Italy. In 2025, a local CHIKV outbreak occurred in Verona province, Veneto Region. We report the findings of integrated epidemiological, virological and entomological investigations. Methods: In 2025, a dedicated surveillance protocol was implemented to assess local transmission of arboviral infections in Verona province, enabling early detection of a local CHIKV circulation. Following notification of the index case, investigations were conducted in accordance with the national and regional arbovirus surveillance plans, including comprehensive epidemiological, virological and entomological analyses. Results: The index case was identified on 6 August 2025, with retrospective detection of the first case with symptom onset on 31 July; the primary case was not identified. As of 15 October, 69 cases were reported (62 confirmed, 7 probable), with a mean age of 55 years; 91.3% had identifiable epidemiological links, mainly clustered in two municipalities of the Verona province. Most cases (76.8%) occurred between mid-August and mid-September. The outbreak lasted approximately 15 weeks, from the end of July to the mid of October. CHIKV-RNA was detectable in whole blood and, less frequently, urine only within the first 5 days after symptom onset, with higher viral loads in blood. CHIKV-specific IgM antibodies were detectable from Days 4–5 and IgG from Days 7–10. A total of 225 Aedes albopictus specimens were collected, all testing negative for CHIKV. Phylogenetic analysis revealed a highly homogeneous, monophyletic cluster within the East-Central-South African genotype, closely related to strains from the 2024–2025 Réunion outbreak. Conclusions: This outbreak underscores the value of dedicated surveillance protocols for early detection of febrile/suspected arboviral cases, while also highlighting key vulnerabilities, namely, an undetected primary case and negative entomological findings, pointing to the need for lower testing thresholds and earlier, risk-based vector sampling.
SN - 1195-1982
SN - 1708-8305
ER -