Eurosurveillance - Volume 30, Issue 46, 20 November 2025

Influenza A(H3N2) subclade K (J.2.4.1) has dominated the 2025/26 season start in England. Post-infection ferret antisera raised against northern hemisphere 2025/26 vaccine strains showed reduced reactivity to subclade K viruses in England, aligning with World Health Organization reports. Nevertheless, early post-vaccination, vaccine effectiveness against influenza-related emergency department attendances and hospital admissions remained within typical ranges, at 72–75% in children and adolescents (< 18 years) and 32–39% in adults. Hence, vaccination remains effective against clinical disease caused by influenza A(H3N2) viruses.

The emergence and spread of an extensively drug-resistant (XDR) Mycobacterium tuberculosis lineage 4.8 cluster in Europe raises public health concerns. First reported in 2020 across Romania, Italy and the United Kingdom, this cluster progressed from multidrug-resistant (MDR) and pre-extensively drug-resistant (pre-XDR) to XDR, including resistance to pretomanid. Evidence of ongoing local transmission is available for Italy, where 10 cases were reported from 2021 to 2025. Strengthened whole genome sequencing-based surveillance is needed to inform timely, coordinated public health responses.

Screening of 54,837 gonococcal genomes identified 12 new variants lacking one (n = 9) or both (n = 3) of the Xpert CT/NG assay’s gonococcal targets. In total, 17 diagnostic-escape variants occurred across five countries and multiple genomic lineages; phylogenomic analysis revealed both ancestral and strain-specific recombination events. Xpert CT/NG diagnostic escape remains rare (0.026%) but illustrates recurrent recombination in gonococci. This emphasises the necessity of continuous external quality assessments, supplementary testing of gonococcal-positive molecular screening samples, and appropriate genomic and epidemiologic surveillance.

In September 2023, a measles outbreak occurred in a middle school (Rhône valley, France), with the index case returning from Asia. Investigations involved case validation, virological analyses, contact tracing and checking vaccination records to determine measles vaccination coverage (VC) and attack rates (AR). Among 643 students, 49 measles cases occurred between 6 September and 18 October 2023 (AR = 7.6%). Two-dose vaccination coverage was 93.5% (601/643). Virological analyses confirmed the measles strains’ clonality (genotype D8) and the imported origin. Concordance between health record vaccination status and immunological profile was established for 27 cases. In a sub-cohort of children (all cases and 309 non-cases), AR was 100% in unvaccinated children, and 43.7%, 16.5% and 3.2% among two-dose vaccinated children with the first dose administered at 6–8, 9–11 and ≥ 12 months, respectively. After multivariate binomial regression, vaccine effectiveness (VE) was 96.4% (95% confidence interval (CI): 91.4–98.5) after two-dose vaccination with the first dose at ≥ 12 months, confirming long-term effectiveness of measles-mumps-rubella vaccines. When the first dose was given at 9–11 and 6–8 months, respectively, VE was 83.3% (95% CI: 74.3–89.2) and 60.7% (95% CI: 10.6–82.7). This measles epidemic mainly affected unvaccinated or two-dose vaccinated children with first dose administered before age 12 months.

We managed a complex outbreak of Shiga toxin-producing Escherichia coli (STEC) and stx-negative E. coli O157 (non-STEC) cases in four nurseries in two neighbouring towns in south-east Scotland, with epidemiological links through shared management, staff or other visits. There were 57 confirmed cases between July and October 2022. Nurseries voluntarily closed to support outbreak control. Subsequent whole genome sequencing identified two separate, unlinked outbreaks of stx2a-positive E. coli O157:H7 (19 confirmed cases in Nursery 1) and stx-negative E. coli O157:H39 (17 confirmed cases in Nursery 2). Smaller numbers of six additional STEC and E. coli O157 (non-STEC) strains were identified in the four nurseries. Five children from Nursery 1 who tested positive for stx2a-positive E. coli O157:H7 required hospitalisation, one of whom developed haemolytic uraemic syndrome. Children with other STEC and E. coli O157 (non-STEC) strains had few or no symptoms. Overall, five of 19 cases with stx2a subtypes were asymptomatic, compared with seven of nine for stx2f subtypes, and 14 of 25 for stx-negative subtypes. Given the findings in this setting, further information on the prevalence of asymptomatic STEC carriage by strain, age and geography, and in other contexts, will support understanding and risk management of future outbreaks.