There was a significant increase in the number of outbreaks and people sick in them in 2022 in the Netherlands, according to recent figures.

In 2022, 1,165 outbreaks were reported, with 4,470 people falling ill. In 2021, there were 838 outbreaks with 3,517 cases. The specific causes of the rise are uncertain but could be due to factors such as better reporting or staff shortages and a lack of knowledge and experience in the industry.

Information on food-related outbreaks comes from the Netherlands Food and Consumer Product Safety Authority (NVWA) and the Municipal Public Health Services (GGDs). NVWA inspects the place where the food was prepared or sold, or where it came from. Wageningen Food Safety Research (WFSR) examines whether the food contains pathogens. The GGDs focus on the infected people to try to find out what caused them to become sick.

An earlier report revealed most foodborne infections increased in the Netherlands in 2022 compared to the year before.

Known agents in outbreaks

A pathogen was identified in patients and/or food or environmental samples in 23 of the 1,165 reports, but the agent was unknown for 1,142 outbreaks.

Salmonella was behind six reported outbreaks; five were due to Campylobacter, and four were linked to norovirus. Shiga toxin-producing E. coli (STEC) caused three epidemics, while Listeria and Shigella sonnei were responsible for one incident each. In one outbreak, Staphylococcus aureus and STEC were suspected, with 30 people sick.

In total, 101 people were affected in the Salmonella outbreaks, 53 in norovirus incidents, 49 in STEC epidemics, and 47 in Shigella outbreaks. Campylobacter outbreaks led to 22 sick people, and the Listeria one had seven cases.

The majority of outbreaks consisted of two to four patients. Next are outbreaks with five to nine patients. There were 17 large outbreaks, with 25 or more patients.

Five of the 23 outbreaks in which a pathogen was detected involved environmental samples. In one outbreak, Listeria was found in monitoring samples, which, thanks to whole genome sequencing, linked to a cluster of patients. During other outbreaks, STEC O157 was found in chicken and mackerel tested positive for Staphylococcus aureus.

Norovirus was detected in oysters during an outbreak where both norovirus and sapovirus were found in patients. It included three groups of people who became ill after eating oysters in restaurants.

In a dozen outbreaks, a pathogen was found only in patients. In an STEC O157 outbreak, a vital link was seen with beef products that might have been eaten raw or not fully cooked, such as filet américain, beef sausage, minced (ground) meat, and hamburgers. Investigations into another outbreak, with 26 cases, pointed to a cake supplied by a local bakery as the likely source.

Multi-year Listeria incidents
The largest outbreak in 2022 was 96 cases from 103 people who had attended a funeral. The cause was not found, but given the reported incubation period of about a day, the pathogen was probably norovirus.

In the Listeria outbreak, with seven cases, people fell ill between August 2022 and January 2023. However, four cases were recorded in August to September 2019 with the same strain. This was traced to a producer of a type of sausage made from liver.

The company was under increased surveillance, and two illnesses were seen in 2020 and 2021. Investigations found the tighter checks had been removed earlier in 2023 and testing found the outbreak strain again in environmental samples. Control measures have once more been taken at the site.

A similar situation occurred at a fish producer. Four cases were from August 2021 to January 2022, linked to monitoring isolates from different types of smoked fish. Further investigation led to a fish processing company, and control actions were taken. Later in the year, another four people fell sick. Listeria strains that fell within the outbreak cluster were found in product and environmental samples at the factory so enhanced steps were implemented.

Between 2017 and 2020, a Listeria strain traced to a salmon producer was seen in one to three patients per year and in product and environmental samples. In December 2021, there were five sick people, and in early 2022, the outbreak strain was found at the producer, prompting measures, including a thorough cleaning, at the site. In the first half of 2022, there were two more patients, and in November 2022, another case was reported.

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