In Belgium, the annual incidence of Listeria monocytogenes infections reported at the National Reference Centre (NRC) ranges between 0.65 and 0.75 cases/100 000 inhabitants over the last ten years. An exceptional high number was notified in 2016 (0.94) mainly due to a multi-country CC8 cluster (UI-492), while the lower number in 2020 (0.47) was probably linked to the Covid-pandemic. Although the number of perinatal cases has been stable, varying between 5 to 10 cases per year, a peak of 16 cases (18.4% of the total number) was reported in 2022. The 6 deaths in utero or after birth and 5 premature births related to these infections, highlight the need to maintain active prevention campaigns among pregnant women.
Since 2020, our NRC has increased its activities to perform real-time sequencing on each isolated strain and thereby augmented its efforts on cluster detection and outbreak investigation. From January 2020 until June 2024, in total 26 genetic clusters were identified for which at least two samples were isolated within a 12 months’ timeframe (≤7 AD, using Moura scheme). 20 of them contain a smaller amount of cases (2-6), while 6 clusters consist of a larger number of cases (8 to 35). 12 clusters are persistent, with strains isolated over a period of more than 2 years (range 2-13 years). Several of these are part of cross-county outbreaks as the Omikron1, Tau1, My2 and Rho8 outbreaks (2020-FWD-00012) linked to fish products. The last numerous outbreak peaked in the winter of 2023-2024 (2023-FWD-00088). In total 22 cases were involved, of which 20 were isolated last winter. Moreover, 2 Dutch and 4 German cases were reported to be related. Investigations by the related food authorities revealed (under-)cooked pig meat (e.g. pâté) as the source of this outbreak, after which actions were taken at the involved firms.
