If two or more people become ill from eating the same food, this is referred to as an outbreak. Since 2016, the number of reports of outbreaks and people becoming ill had kept increasing (with the exception of 2020, the first year of the COVID-19 pandemic). In 2023, the number of reports of outbreaks and people becoming ill was, for the first time, lower than the year before.

Cause often unknown

The exact cause of an outbreak of foodborne infections often remains unknown, as it is not always clear which food product was contaminated or which pathogen caused the symptoms. In cases where the cause is known, the bacteria Salmonella and Campylobacter are responsible for most of the outbreaks.

Gaining insight into causes

Reports of outbreaks of foodborne infections are made by the Netherlands Food and Consumer Product Safety Authority (NVWA) and the Municipal Public Health Services. RIVM combines these reports in order to conduct research into foodborne infections. The Municipal Public Health Services try to identify the causes with the help of people who may have become ill from eating contaminated food. The NVWA examines the place where the food was prepared or sold, or where the food came from. Where necessary, the NVWA also asks Wageningen Food Safety Research (WFSR) to look for pathogens in the food. If the cause is found, the NVWA can remove a product from the market or take measures to prevent repeat infections. This way, fewer people will become ill from eating contaminated food.

Salmonella in eggshells

In 2023, there was a large-scale outbreak of Salmonella infections, probably caused by people eating contaminated eggs. The Municipal Public Health Services received reports of more than 160 patients with a Salmonella infection who had sought medical care. In reality, the number of people who had become ill was much higher, as most people with a Salmonella infection do not require medical care. Together with the NVWA, the Dutch supervisory authority in the field of dairy, poultry and eggs (COKZ), the Municipal Public Health Services and other organisations, RIVM investigated where the contaminated eggs originated from. It turned out that contaminated eggshells had been processed into animal feed. As a result, chickens at multiple laying hen farms had become contaminated. To prevent Salmonella bacteria in eggshells from contaminating animal feed for chickens a second time, the NVWA tightened supervision of the processing of eggshells in the animal feed industry. The outbreak had passed by early 2024.

Preventing foodborne infections

The data of the NVWA, the Municipal Public Health Services and WFSR provides insight into the causes of outbreaks. It also indicates the prevalence of outbreaks and possible changes over the years. This allows RIVM to advise people on what they themselves can do to avoid becoming ill from eating contaminated food. Good hygiene is highly recommended. This includes washing your hands before preparing food and keeping food that has already been prepared separate from food that has not yet been prepared. Heating food or keeping it cool can also help prevent foodborne infections.