Eurosurveillance - Volume 30, Issue 37, 18 September 2025

To spot potential introductions of West Nile virus (WNV) into Denmark, a national surveillance programme for WNV was established in 2011. The relevance of this programme was underscored in the late 2010s, when WNV was detected in areas close to Denmark.

We describe the Danish WNV surveillance programme and its findings in 2011−2023.

The surveillance programme monitors mosquitoes, which are WNV vectors, and some mammalian animals and birds, which are WNV hosts. Surveillance samples are also tested for the closely related Usutu virus (USUV), which, like WNV, is a flavivirus. During the study, WNV and USUV RNAs were sought in 62 bats (sampled in 2022−2023), 5,661 Culex sp. mosquitoes (2011−2023), 628 dead wild birds (2011−2014 and 2019−2023), and 492 live birds (2011−2012, 2022−2023). These 492 birds were from among 3,269 live long-distance migratory birds (sampled in 2011−2023) serologically tested for WNV and USUV antibodies. Additionally, 4,978 free-ranging poultry (2011−2023) and 236 horses (2011−2013) were tested serologically.

Neither WNV nor USUV RNA was detected in bats, mosquitoes, or birds, but anti-WNV specific antibodies were detected in migratory birds, one domestic chicken and one imported horse. For migratory birds, competitive ELISAs detected anti-flavivirus antibodies in 3.9% (128/3,269) of tested samples. Across 2011−2023, the annual flavivirus seroprevalence varied from 1−13%. Using virus neutralisation assays on selected samples, anti-WNV or anti-USUV specific antibodies were detected in 25 and 11 bird samples, respectively.

Findings demonstrate that the concern about virus incursion is well founded and support continued vigilance for WNV.

Tuberculosis (TB) is curable and preventable, yet remains a health concern in vulnerable populations. Individuals experiencing homelessness are at increased risk owing to medical, environmental and social factors.

We aimed to evaluate a 20-year TB screening programme in people experiencing homelessness in Brno, Czechia (2005–2024), and analyse additional TB diagnoses in this population made outside the project, to inform public health strategies for TB control in vulnerable groups in a low-incidence country.

Clinical examination and chest X-ray screening were offered to people without stable housing, incentivised by meal vouchers. Individuals with pathological findings underwent further diagnostic evaluation and treatment. Demographic and clinical data were collected. Additional TB diagnoses made in this population through other detection methods were analysed for comparison.

Between 2005 and 2024, of 3,918 individuals approached, 2,664 participated in screening (average participation rate: 68.0%), and 18 were diagnosed with TB through the project. Another 132 individuals experiencing homelessness were diagnosed with TB through other pathways, yielding 150 diagnoses, representing 19.3% of TB notifications in Brno. The estimated TB incidence among people experiencing homelessness was 24.4 times higher than in the general population (95% confidence interval: 20.5–28.9). Despite a citywide decline in TB incidence, the proportion of TB diagnoses among people who experience homelessness increased over time.

Homelessness is a risk factor for TB in low-incidence settings. This long-term screening initiative proved feasible and valuable, demonstrating how outreach-based screening can support early detection and contribute to TB prevention among socio-economically marginalised populations.