Eurosurveillance - Current Issue -Volume 30, Issue 22, 05/Jun/2025

Swine influenza has a considerable impact on pig populations and poses a pandemic threat to humans. However, little is known about the influenza A viruses circulating among pigs in the Netherlands.

We piloted a surveillance programme aimed at enabling swine influenza A virus (swIAV) surveillance in the Netherlands: investigated prevalence, genomic characteristics and recent evolution of circulating swIAV variants and compared them with relevant human and swine influenza viruses from the Netherlands and other European countries.

We collected and tested respiratory samples from pigs (2019–2023) for swIAV, characterised the viruses with molecular and virological methods and shared molecular data of swine and relevant human influenza A viruses in a national platform.

We detected swIAV throughout the year in 342 (42%) of 824 respiratory samples from 90 farms. Complete genome sequencing identified 73 H1N1, 51 H1N2 and one H3N2 viruses. Phylogenetic analyses identified viruses from each of the three H1 swine lineages (1A/B/C) and four subclades. Viruses from the 1A lineage clustered into three subgroups with distinct antigenic properties, which seemed descendent from separate introductions of human seasonal A(H1N1)pdm09 viruses. Phenotypically, no reduced susceptibility to existing antiviral drugs oseltamivir and zanamivir was found.

We provided insights into swIAVs in pigs in the Netherlands, including antiviral susceptibility and antigenic differences. It highlighted occasional virus transmission between humans and pigs. Sharing swIAV data at a national level will be continued to reduce influenza burden in swine and support identification and characterisation of emerging swIAVs with zoonotic potential.

Most Toxoplasma gondii infections in humans are considered foodborne, but the relative importance of the various routes of infection is largely unknown. Consumption of green produce contaminated with T. gondii oocysts has been identified as a possible source.

We aimed to estimate the occurrence and prevalence of T. gondii oocysts in commercially available ready-to-eat (RTE) salad mixes in 10 European countries.

A real-time PCR-based method for oocyst detection was developed and optimised by two laboratories and validated in an interlaboratory test. This detection method and a harmonised sampling strategy were applied in a multi-country study. Multivariable logistic regression was used to investigate risk factors for oocyst contamination of RTE salad.

The real-time PCR method had a detection limit of 10 oocysts per 30 g of salad. We collected 3,329 RTE salad samples (baby leaf and cut leaf mixes) from October 2021 to September 2022. The prevalence of T. gondii oocyst contamination was 4.1% (95% confidence interval (CI): 3.4–4.8%; n = 3,293). In multivariable regression analysis, winter season, sampling and packaging of salad in Northern Europe and production of salad in Western Europe were associated with detection of T. gondii, with no statistically significant differences between salad types.

We estimated the prevalence of T. gondii oocysts in RTE leafy green salads using a validated and standardised procedure to assess the potential risk for human infection; highlighting the need to address this risk at each critical point of the salad production chain.

During the COVID-19 pandemic, Santé publique France (SpF) published incidence (SpFi) rates based on census denominators. Denominators using cell phone connection (CPC) data can better reflect the population present and seasonal mobilities.

Given uncertainties regarding the actual number of Île-de-France (IdF) residents present in IdF during summer 2021, we aimed to better approximate true incidence rates from positive SARS-CoV-2 tests in IdF using CPC-derived population denominators.

This longitudinal study used the daily number of positive tests (PCR and Ag) on IdF residents in IdF as the numerator and the estimated resident population present in IdF at midnight as the denominator. We computed the mean corrected incidence rate (MCIR) per moving week between 4 July and 9 September 2021.

The MCIR showed higher incidence rates than initially estimated, especially during August when residents had left IdF for the holidays. Incidence rates reached a peak on 16 August when the SpFi rate per moving week was 200.9 per 100,000 compared with 315.6 per 100,000 with the MCIR, representing a 57% increase.

Using local SARS-CoV-2 testing data and real-time population denominators, we showed that indicators using non-geographically referenced test results and fixed population denominators that ignore seasonal mobility can significantly underestimate incidence rates in IdF. New data sources using CPC data provide the opportunity to calculate more accurate and dynamic incidence rates and to map epidemics more precisely and in real time.