Eurosurveillance - Volume 31, Issue 22, 04 June 2026

West Nile virus (WNV) is a zoonotic mosquito-borne pathogen increasingly reported in Europe.

We aimed to characterise heterogeneities in the average annual human risk of WNV infection (force of infection, FOI) and in WNV surveillance across Europe.

We conducted a systematic review following the PRISMA guidelines to identify serological studies on WNV in humans with IgG-based assays in Europe. We then used mathematical models fitted to both age-stratified serosurvey and case data to reconstruct spatially explicit FOI estimates, the sensitivity of syndromic surveillance and age-dependent trends in case reporting.

We extracted 92 serosurvey datasets from 21 countries. Based on 10 age-stratified serosurvey datasets from Greece, Hungary, Italy, Romania and Spain and case data from seven countries (Austria, Cyprus, Greece, Hungary, Italy, Romania and Spain), we estimated the WNV FOI for 119 European nomenclature of territorial units for statistics level (NUTS) 0-3 regions. We found evidence of spatial heterogeneities in transmission intensity and estimated that on average less than 0.2% of human WNV infections were notified, with country variability and age-dependent trends in the propensity of reporting WNV disease.

This study shows that the intensity of WNV transmission, the average annual incidence of infection and the sensitivity of surveillance are heterogeneous across Europe. Due to differences in case reporting across countries, the incidence of reported WNV cases does not necessarily reflect the same proportion of WNV infections and hence the actual infection incidence, which highlights the importance of conducting WNV seroprevalence surveys.

With a notification rate of 44.9 per million population in 2024, Belgium was among the countries with the highest measles rate of the European Union/European Economic Area countries. Although the coverage of the first dose of measles–mumps–rubella (MMR) vaccination in Flanders was 96% in 2020, two-dose coverage was below 95%. To minimise the risk of sustained measles transmission in vulnerable settings, such as primary schools with low vaccination coverage or daycares, it is important to quarantine susceptible contacts of a measles case.

We aimed to identify policies that balance measles outbreak control with societal as well as educational impact of quarantining children.

Using a simulation model, we evaluated the impact of different quarantine strategies for measles in primary school and daycare settings in Flanders, Belgium.

We found that shortening the quarantine period from 21 to 18 days only moderately (e.g. 16–37% in primary school) increased the risk of a subsequent infection wave, and the final proportion of later-generation cases remained at most 3.2% of the school or daycare. In settings with a low vaccination coverage (e.g. 20%), multiple independent introductions or a low diagnosis rate (e.g. only half of symptomatic children going to a doctor), the addition of post-exposure vaccination can further reduce transmission risk.

We found that quarantine duration could be shorter than the presumed maximal incubation period of 21 days, without substantially increasing the risk of onward transmission. As such, acceptability and compliance with mandated quarantine periods might also increase.

From 1 March 2020, the Centre for Sexual Health Amsterdam limits presumptive treatment for chlamydia or gonorrhoea to clients notified by steady partners. Treatment after notification by non-steady partners requires a positive test result.

We aimed to evaluate this change in policy on unnecessary antibiotic treatment, time to treatment and lost to follow-up clients.

We included consultations (with testing) following partner notification for chlamydia or gonorrhoea between 1 March 2017 and 1 March 2023. Primary outcome was unnecessary antibiotic treatment (presumptive treatment with negative test result) before vs after the policy change. We also assessed return for treatment of confirmed and not presumptively treated individuals after the policy change.

From 4,579 consultations, unnecessary antibiotics were prescribed for 786/1,318 (59.6%) clients for chlamydia and 729/1,117 (65.3%) clients for gonorrhoea before 1 March 2020. After 1 March 2020, this decreased to 324/1,275 (25%) and 341/1,369 (25%), respectively, corresponding to a relative reduction of 58% for chlamydia (adjusted relative risk (aRR): 0.42; 95% confidence interval (CI): 0.37–0.47) and 63% (aRR: 0.37; 95% CI: 0.33–0.42) for gonorrhoea. After the policy change, clients not given presumptive treatment but later diagnosed returned after a median of 7 days (interquartile range (IQR): 5–8) for chlamydia and 6 days (IQR: 4–7) for gonorrhoea. Missed treatment occurred in 4/155 (2.6%) of chlamydia and 5/158 (3.2%) of gonorrhoea consultations.

The new partner management protocol substantially reduced unnecessary antibiotic treatment for chlamydia and gonorrhoea. The majority of confirmed infections still received appropriate treatment.