Detection of dengue virus serotype 2 in local Aedes aegypti populations, Madeira Island, Portugal, 2025
File(s)
Published version
Author(s)
Type
Journal Article
Abstract
Background
Since 2010, dengue virus (DENV) has caused sporadic outbreaks across Europe, namely in Croatia, Spain, France, Italy and the Portuguese island of Madeira. Aedes aegypti mosquito is established in the Autonomous Region of Madeira, and along the eastern Black Sea coast of Cyprus. In Madeira Island, an outbreak of DENV serotype 1 occurred between 2012 and 2013, resulting in 1080 confirmed cases. Despite ongoing entomological surveillance, no further local transmission was detected in the following decade.
Methods
In January 2025, following two suspected dengue cases on Madeira Island, increased entomological surveillance efforts were implemented to confirm a local event transmission of DENV. A network of mosquito traps was complemented by targeted surveillance using 17 BG-PRO traps positioned in the vicinity of suspected human cases. Daily collections of adult A. aegypti, collected from 10 January to 31 March 2025, were screened by reverse transcription polymerase chain reaction (RT-PCR) for Aedes-borne viruses in the reference laboratory. Viral sequencing was performed using target enrichment and bioinformatics with INSaFLU-TELEVIR. The climate-driven suitability for dengue transmission by A. aegypti was also investigated. Serological and molecular tests were conducted on samples from suspected human cases.
Results
Out of 80 analysed A. aegypti pools (N = 393 mosquitoes), 1 pool, with 9 mosquitoes collected near the home of suspected human cases, tested positive for DENV. The dengue whole genome sequence from this sample was determined and classified as DENV-2 lineage 2II_F.1.1.3. The same virus was retrospectively confirmed in one of the clinical cases. Analysis of mosquito abundance and climate data confirmed the occurrence of this local transmission event during a period of low mosquito abundance and low climatic suitability.
Conclusions
Here, we report an in-depth analysis of a local dengue transmission event that occurred in Funchal, the capital of Madeira Island, in January 2025, with whole-genome evidence of DENV-2II_F.1.1.3 in field-caught A. aegypti mosquitoes. Retrospective analysis confirmed the presence of the same virus in one of the two clinical cases, establishing a direct link between human and mosquito infections, and highlighting the risk of off-season arboviral introductions.
Since 2010, dengue virus (DENV) has caused sporadic outbreaks across Europe, namely in Croatia, Spain, France, Italy and the Portuguese island of Madeira. Aedes aegypti mosquito is established in the Autonomous Region of Madeira, and along the eastern Black Sea coast of Cyprus. In Madeira Island, an outbreak of DENV serotype 1 occurred between 2012 and 2013, resulting in 1080 confirmed cases. Despite ongoing entomological surveillance, no further local transmission was detected in the following decade.
Methods
In January 2025, following two suspected dengue cases on Madeira Island, increased entomological surveillance efforts were implemented to confirm a local event transmission of DENV. A network of mosquito traps was complemented by targeted surveillance using 17 BG-PRO traps positioned in the vicinity of suspected human cases. Daily collections of adult A. aegypti, collected from 10 January to 31 March 2025, were screened by reverse transcription polymerase chain reaction (RT-PCR) for Aedes-borne viruses in the reference laboratory. Viral sequencing was performed using target enrichment and bioinformatics with INSaFLU-TELEVIR. The climate-driven suitability for dengue transmission by A. aegypti was also investigated. Serological and molecular tests were conducted on samples from suspected human cases.
Results
Out of 80 analysed A. aegypti pools (N = 393 mosquitoes), 1 pool, with 9 mosquitoes collected near the home of suspected human cases, tested positive for DENV. The dengue whole genome sequence from this sample was determined and classified as DENV-2 lineage 2II_F.1.1.3. The same virus was retrospectively confirmed in one of the clinical cases. Analysis of mosquito abundance and climate data confirmed the occurrence of this local transmission event during a period of low mosquito abundance and low climatic suitability.
Conclusions
Here, we report an in-depth analysis of a local dengue transmission event that occurred in Funchal, the capital of Madeira Island, in January 2025, with whole-genome evidence of DENV-2II_F.1.1.3 in field-caught A. aegypti mosquitoes. Retrospective analysis confirmed the presence of the same virus in one of the two clinical cases, establishing a direct link between human and mosquito infections, and highlighting the risk of off-season arboviral introductions.
Date Issued
2026-02-18
Date Acceptance
2026-01-07
Citation
Parasites and Vectors, 2026, 19 (1)
ISSN
1756-3305
Publisher
BMC
Journal / Book Title
Parasites and Vectors
Volume
19
Issue
1
Copyright Statement
© The Author(s) 2026. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data
License URL
Identifier
10.1186/s13071-026-07251-1
Subjects
Dengue virus
Aedes aegypti
Madeira Island
Surveillance
Publication Status
Published
Article Number
92
Date Publish Online
2026-01-27