Growing number of Salmonella cases in the Netherlands

What started as a major outbreak in 2023 has now turned into a persistent issue. The number of Salmonella Enteritidis infections in the Netherlands continues to rise—both among people and on laying hen farms. And that’s cause for concern, also among regulators.

More human cases reported

In 2023, the number of confirmed infections reached 427. That’s a sharp increase compared to the pre-COVID years, when the average was around 281. The figures remained high in 2024 (401 reports), and the first half of 2025 has already seen 209 cases. That alone is twice the average for this time of year. Cases involving recent travel abroad have not been included in these numbers.

The 2023 outbreak, which accounted for 151 cases, was most likely caused by contaminated eggshells. These originated from SE-positive laying hen farms but were not properly heat-treated before being added to poultry feed. As a result, new flocks were infected. And later on, so were people, through eggs.

Smaller outbreaks, harder to trace

In 2024 and 2025, researchers have mainly observed smaller clusters. RIVM identified 38 in 2023, 42 in 2024, and already 22 in the first half of 2025. On average, each cluster involved three cases. Small numbers, but spread across the country.

Genetic research also shows that strain diversity is increasing. That makes it harder to identify sources and apply targeted control measures. According to RIVM, the pattern points to widespread transmission, without a clear source or classic outbreak location. In early 2025, a Zoonoses Response Team (RT-Z) was set up. Among their recommendations: test flocks more frequently, remove positive groups more quickly, and monitor genetics across the chain, from barn to feed.

Number of infected farms has doubled

The poultry sector shows the same trend. Between 2018 and 2022, an average of 30 infected flocks were found per year. In 2023, that number jumped to 74. In 2024, even to 81. And by mid-2025, the count has already reached 50. One possible reason? Laying hens are kept in production longer these days. As they age, vaccine protection can decline. That makes them more susceptible to infection, and increases the risk of farm-to-farm transmission.

At the European level, things still appear relatively stable. So far, the situation seems unique to the Netherlands. Other EU countries have not reported a similar rise. But that says little about what may still lie ahead.

Eurosurveillance.org