Between 2020 and 2025, Cu/ex surveillance was conducted in 17 of the 26 countries that responded to the questionnaire, while control measures were implemented in 12 countries. Among countries conducting surveillance, WNV was most often reported as a public and/or veterinary health concern, and surveillance activities were commonly described as informing response efforts. The questionnaire findings also show substantial variation in how surveillance and control activities are organised and implemented across countries. This variation reflects differences in national governance structures, legal mandates and the distribution of responsibilities between national, regional and local levels. The main reported objectives of Cu/ex surveillance were outbreak investigation and assessment of the level, location and timing of transmission risk. Funding for Cu/ex surveillance was often reported as limited in duration or project-based: only seven of the 17 countries conducting surveillance reported that outbreak-related surveillance activities were embedded in a long-term strategy (exceeding three years) for disease risk assessment and control. Countries reported using a range of control methods, with adult mosquito control using biocides being the most frequently reported approach.
Between 2020 and 2025, Aedes invasive mosquito surveillance was conducted in 20 of the 26 responding countries, and control activities were implemented in 17 countries. Surveillance was mainly used to assess the introduction and spread of invasive Aedes species. In several countries, it was also used to inform response efforts or to address public or veterinary health concerns. As with Cu/ex mosquitoes, the organisation and implementation of Aedes mosquito surveillance and control varied across countries, reflecting differences in institutional structures, responsibilities and risk contexts. Some countries reported that preventive control was embedded in long-term strategies for disease risk reduction, while reactive control was often funded on an ad hoc basis. For elimination efforts following introductions, the funding mechanism was unclear or unknown in several countries. Respondents reported using a range of methods to control Aedes mosquitoes. Preventive and elimination measures commonly targeted immature stages and included both biocidal and non-biocidal interventions, often combined with formalised social mobilisation programmes. Reactive control, by contrast, was more often reported as targeting adult mosquitoes using biocides.
Previous work has identified several challenges related to vector surveillance and control in Europe. The ECDC report 'Organisation of Vector Surveillance and Control in Europe', published in 2021, described constraints including limited human and financial resources, complex organisational structures within countries, insufficient inter-governmental and inter-institutional cooperation, and unclear roles and responsibilities in the organisation and implementation of vector surveillance and control [1]. Similarly, the AIM-COST survey on Aedes invasive mosquito surveillance and control highlighted challenges related to limited political support, insufficient funding, shortages of trained personnel and weak coordination across governance levels [7]. It also reported that surveillance data were often underused in planning and that international guidance, although widely used, was not always well adapted to local contexts. The findings from the current questionnaire are consistent with several of these previously identified challenges, particularly in relation to funding, training, coordination, clarity of responsibilities, use of surveillance data, guidance and capacity-building.
The questionnaire findings are discussed below under four main themes: responsibilities and coordination, resources, legal and regulatory issues, and operational topics.