Introduction
Sciensano, which harbors the National Reference Laboratory for Food-borne outbreaks, collects and centralizes the information on food-borne outbreaks (FBOs) and assures the follow-up of the FBOs in Belgium.
Materials and Methods
A food-borne outbreak is defined as an incidence, observed under given circumstances, of two or more human cases of the same disease and/or infection, or a situation in which the observed number of human cases exceeds the expected number and where the cases are linked, or are probably linked, to the same food source (Directive 2003/99/EC, Article 2(d)). Food-borne outbreaks are registered in the national system and reported to EFSA.
Results and Discussion
In 2023, a total of 722 outbreaks were reported. The most common causative agents were norovirus, pathogenic E. coli (STEC), Bacillus cereus and Salmonella, responsible for 15, 14, 7 and 7 food-borne outbreaks, respectively, leading to 478, 42, 60 and 38 illnesses. A total of 716 outbreaks were classified as weak-evidence outbreaks. Six outbreaks were strong-evidence outbreaks because the causative agent was detected in the implicated food and/or a strong epidemiological link was established with a specific food product. Three of these strong-evidence outbreaks were caused by norovirus: two outbreaks were linked to oysters and one to cut carrots. One STEC outbreak was a multi-country outbreak affecting France and Belgium (2023-FWD-00029), caused by pathogenic E. coli O26:H11, with the source identified as raw fermented milk produced in Belgium. The number of Belgian cases formally linked with the outbreak includes two cases in 2023 and one case in 2022 (identified through retrospective WGS analysis). B. cereus was involved in two strong-evidence outbreaks resulting in 15 and 17 illnesses, respectively. In the first outbreak, which occurred after a wedding buffet, enterotoxigenic B. cereus was isolated from a bread sample, a swab taken from a work surface and one clinical sample (stool). In the second outbreak, which affected two schools supplied by the same central kitchen, emetic B. cereus and its emetic toxin were detected in semolina samples as well as in one stool sample. Listeria monocytogenes 4b CC1 ST10 was responsible for one multi-country outbreak (2023-FWD-0088) with cases disseminated in Belgium (14 cases in 2023, mostly in Flanders) as well as in The Netherlands and Germany.
In 92% of the outbreaks (n=661 out of 722), no causative agent could be identified. This can be attributed to the absence of food leftovers in most of the outbreaks and/or late reporting by the consumer. In 18% of the outbreaks, human and/or food samples were sent for analysis, and 48% of these (n=61) resulted in the detection of a pathogen. This highlights the importance of rigorous sampling of suspected food and environmental samples and the added value of microbiological results for foodborne outbreak investigation.
