Eurosurveillance - Volume 30, Issue 1, 09 January 2025

Early detection and characterisation of SARS-CoV-2 variants have been and continue to be essential for assessing their public health impact. In August 2023, Santé publique France implemented enhanced surveillance for BA.2.86 and sub-lineage JN.1 because of their genetic divergence from other variants and increased prevalence.

To detail how combining epidemiological and laboratory data sources, targeted investigations and modelling enabled comprehensive characterisation of sub-lineage JN.1.

Data were collected from epidemiological investigations using a standardised questionnaire and from routine and novel (RELAB network) surveillance systems. JN.1 cases were compared with cases infected with previously circulating variants, such as EG.5, BA.4/BA.5 and other BA.2.86 sub-lineages. The growth rate and doubling time of JN.1 were estimated.

JN.1 was first detected in September 2023 in the Île-de-France region, France, and spread widely across the country. By late November, doubling time was estimated to be 8.6 to 26.4 days depending on the region. For all data sources, cases infected by JN.1 showed similar demographics, rates of hospitalisation and RT-PCR cycle threshold values compared with those infected by previous variants. JN.1 cases also had older median age (54 years; 40–71 vs 47 years; 30–59), more frequent reports of feverish feeling and less frequent cough or nausea compared with BA.4/BA.5 cases. JN.1 cases had significantly higher frequency of anosmia compared with other BA.2.86 cases.

Combining different data sources played a key role in detecting emerging variant JN.1, for which no evidence of increased public health impact was found despite its genetic divergence.

Clostridioides difficile infection (CDI) is a severe infection that needs to be monitored. This infection predominantly occurs in hospitalised patients after antimicrobial treatment, with high mortality in elderly patients.

We aimed at estimating the incidence of CDI in Italian hospitals over 4 months in 2022.

We estimated incidences of hospital-acquired CDI (HA-CDI), community or unknown CDI (CA/UA-CDI), recurrent CDI and overall CDI in 25 Italian hospitals, characterised C. difficile isolates using PCR ribotyping, analysed them for toxin genes and susceptibility to antimicrobials.

Clostridioides difficile was detected in 9.7% (655/6,722) of samples from 550 patients, 18 patients died of CDI. The mean overall CDI incidence was 5.0 cases per 10,000 patient days (range: 0.7–11.9). For HA-CDI, mean incidence was 3.7 (range: 0.7–9.2), for CA/UA-CDI 0.8 (range: 0.0–3.2) and for recurrent CDI 0.5 (range: 0.0–3.4). Most patients were female (n = 295; 53.6%), aged ≥ 65 years (n = 422; 76.7%) and previously hospitalised (n = 275; 50.0%). Of the 270 culturable isolates, 267 (98.9%) had toxin A and B genes and 51 (18.9%) the binary toxin genes. Of the 55 PCR ribotypes (RTs) identified, RT 018 (n = 56; 20.7%) and RT 607 (n = 23; 8.5%) were the most common, RT 607 in the northern (p < 0.0001) and RT 018 in the central (p < 0.0001) regions of Italy. Most isolates (n = 158; 58.5%) were antimicrobial-resistant and 119 (44.1%) were multidrug-resistant (MDR).

Highly virulent and MDR C. difficile types are circulating in Italian hospitals which highlights the need of robust surveillance and stringent prevention and control measures.

The first Corona Monitoring Nationwide (RKI-SOEP) study (October 2020−February 2021) found a low pre-vaccine SARS-CoV-2 antibody seroprevalence (2.1%) in the German adult population (≥ 18 years).

The objective of this second RKI-SOEP (RKI-SOEP-2) study in November 2021−March 2022 was to estimate the prevalence of SARS-CoV-2-specific anti-spike and/or anti-nucleocapsid (anti-N) IgG antibodies (combined seroprevalence), past infection based on infection-induced seroprevalence (anti-N), and basic immunisation (at least two antigen contacts through vaccination or infection) in individuals aged ≥ 14 years. We also aimed to estimate under-reporting of infections.

Dried blood-spot specimens from a population-based sample embedded in a dynamic cohort, the Socio-Economic Panel (SOEP), were serologically analysed. Resulting serological data and self-reports via a questionnaire from the same individuals were used to estimate prevalences.

Combined seroprevalence was 90.7% (95% CI: 89.7%–91.6%) without correction and 94.6% (95% CI: 93.6%–95.7%) with correction for sensitivity/specificity and antibody waning. While one in nine individuals had been infected (11.3%; 95% CI: 9.1%–13.5%), nine in 10 had a basic immunisation (90%; 95% CI: 88.9–90.9%), primarily due to vaccination. Population-weighted estimates differed by age, region, and socioeconomic deprivation. The under-reporting factor was estimated as 1.55 (95% CI: 1.3–1.8).

When the SARS-CoV-2-Omicron wave was beginning, most people had been vaccinated, infected, or both. Large-scale vaccination, but not a high infection rate, was able to fill the immunity gap, especially in ≥ 65 year-olds who are known to be at higher risk of severe COVID-19. Our data point towards the need for targeted socioeconomically, demographically and regionally stratified mitigation strategies, including measures to enhance vaccine uptake.