Eurosurveillance - Volume 30, Issue 7, 20 February 2025

We report an adenovirus outbreak with unusually severe clinical presentation, particularly in military conscripts and their close contacts. During 1 February–30 June 2024, 129 patients with adenovirus infection were hospitalised, 30 were admitted to ICU, 10 required ECMO treatment and six died. Cases consisted of 75 conscripts (58.1%) and 54 civilians (41.9%). Most samples were type 7 (97/108; 89.8%); all 24 sequenced samples were subtype 7d. During 1 August–30 November 2024, 274 additional hospitalised cases were identified from registries.

The 2024/25 influenza season in Europe is currently characterised by co-circulation of influenza A(H1N1)pdm09, A(H3N2) and B/Victoria viruses, with influenza A(H1N1)pdm09 predominating. Interim vaccine effectiveness (VE) estimates from eight European studies (17 countries) indicate an all-age influenza A VE of 32–53% in primary care and 33–56% in hospital settings, with some signals of lower VE by subtype and higher VE against influenza B (≥ 58% across settings). Where feasible, influenza vaccination should be encouraged and other prevention measures strengthened.

Influenza circulates at high levels in Europe since November 2024. Using a test-negative study based on data from French community laboratories between October 2024 and February 2025, we estimated vaccine effectiveness (VE) against PCR-detected influenza infection (44,420/15,052; positive/negative individuals). For all age groups, the overall VE was 42% (95% CI: 37–46%), with 26% (95% CI: 18–34%) against influenza A and 75% (95% CI: 66–82%) against influenza B. Among individuals ≥ 65-year-olds VE was 22% (95% CI: 13–30%) and among 0–64-year-olds, 60% (95% CI: 56–65%).

We estimated early influenza vaccine effectiveness (VE) for the 2024/25 season in outpatients, in Beijing using a test-negative design. A(H1N1)pdm09 dominated (99.3%), all sequenced strains (n = 38) clustered in clade 6B.1A.5a.2a, and 37 of 38 antigenically similar to the vaccine strain. VE against any influenza virus infection was 48.5% (95% CI: 34.8–59.5) and 48.7% (95% CI: 35.1–59.7) against A(H1N1)pdm09. Vaccination in the current or previous season against any influenza showed a VE of 52.5% to 54.9%, compared to no vaccination in both seasons.

Listeria monocytogenes can cause severe illness in individuals with weakened immune systems. In March 2023, L. monocytogenes was isolated from blood (n = 2) or pleural fluid (n = 1) of three febrile patients receiving synthetic glucocorticoids in a tertiary hospital in Germany. Food supply records suggested sliced parboiled sausage as the likely source, and L. monocytogenes was isolated from four samples of sealed packaged sliced sausages and ham from one manufacturer. The patient and food isolates clustered within 0–4 allelic differences. Counts of L. monocytogenes in all four food samples were < 100 colony-forming units (CFU)/g, a threshold in the European Union legislation for ready-to-eat products with specific conditions. Our findings, aligned with previous evidence, highlight that persons with weakened immune systems should not be exposed to L. monocytogenes in food. We advocate for a clear communication of deli meats as high-risk foods, so individuals with weakened immune systems can adjust their diet to reduce their risk for invasive listeriosis. We recommend an update of dietary and hygiene guidelines for care settings and private homes where food is prepared, handled and stored for persons with weakened immune systems.