Eurosurveillance - Volume 31, Issue 10, 12 March 2026

In the Netherlands, locally acquired animal and human cases of West Nile virus (WNV) were first identified in 2020 via multidisciplinary WNV monitoring and research activities focusing on mosquitoes, birds, horses, and humans.

We investigated how different activities contributed to WNV detection and response in the Netherlands between 2020 and 2023, to determine best practices, challenges, and opportunities for improvement.

We identified WNV monitoring and research activities in the Netherlands from 2020 to 2023 and analysed their timeliness to detect and react to WNV circulation. An after-action review (AAR) was conducted with national WNV experts to assess best practices and challenges in the multidisciplinary approach.

In 2020, WNV circulation was discovered in an infected bird through a wild live bird research survey and subsequently through mosquito research and monitoring. Thirty-five days after finding the WNV-PCR-positive bird, the first autochthonous human case was uncovered. Between 2021 and 2023, research projects in animals, including sentinel chickens, detected ongoing local enzootic WNV circulation. The AAR highlighted rapid information sharing and interpretation, enabled by multidisciplinary collaborations, as best practice. However, differing institute priorities could sometimes lead to diverging views on follow-up actions.

Research and monitoring activities in mosquitoes and animals, particularly wild birds and sentinel chickens, enabled early detection of WNV circulation. Real-time testing could provide early warning of human cases, enabling timely responses. Therefore, these research and monitoring activities should be maintained. Multidisciplinary collaboration enabled rapid detection and response, and addressing remaining challenges could further strengthen effectiveness.

Enteroviruses cause symptoms ranging from mild skin manifestations to severe neurological diseases, such as polio. Despite global eradication efforts, poliovirus was detected via environmental surveillance in multiple European countries in 2024 and 2025.

We aimed to assess the epidemiology of enteroviruses in Denmark, using national laboratory surveillance and hospital discharge registries, and to determine the accuracy of enterovirus registration.

Hospital admission data from 1 January 2010 to 31 December 2023 were linked to laboratory surveillance enterovirus data to identify and categorise admissions with an enterovirus-specific ICD-10 code and/or enterovirus-positive test. The accuracy of diagnosis coding and positive enterovirus tests was assessed against an estimated ‘true population’ using a capture‒recapture analysis.

Among patients with an ICD-10 enterovirus code and a positive enterovirus test (n = 1,186), 69% had a central nervous system diagnosis. Patients with ICD-10 enterovirus codes only (n = 3,434) were younger and primarily had hand, foot and mouth disease. Patients positive for enterovirus without an enterovirus diagnosis (n = 3,263) frequently exhibited respiratory symptoms. The combined accuracy of ICD-10 codes and enterovirus tests was 46.3% (95% confidence interval (CI): 44.3–48.4) against an estimated ‘true population’ of 28,193 (95% CI: 26,929–29,457) enterovirus infections.

CONCLUSION: It is important to combine laboratory data and ICD-10 codes to gain comprehensive understanding of the enterovirus epidemiology and identify areas for improvement in enterovirus surveillance. Despite exceptional registries, the Danish system may still overlook early cases of emerging or severe enterovirus infections because of limited clinical awareness of these infections and the challenges associated with voluntary test registrations.