Introduction

A multi-country outbreak caused by monophasic Salmonella Typhimurium is presented. A link with chocolate products from a Belgian factory was established by epidemiological, microbiological and traceback investigations. Whole genome sequencing (WGS) analysis of human and food isolates revealed the presence of two clusters:  HC5_296366 (cluster 1) and HC5_298160 (cluster 2).  The investigation of the outbreak as well as  measures taken are presented.

Materials and Methods

Probable and confirmed cases were identified using ECDC case definitions. Raw materials and finished food products collected at the factory were analysed for Salmonella spp. using ISO 6579-1:2017 and real-time PCR. WGS analysis of selected food and human isolates was performed.

Results & Discussion

In Belgium 64 confirmed and 2 probable cases were identified (89% children aged 1-9 years old, 43% hospitalizations), with illness onset from mid-January until April and a peak in cases mid-February 2022. WGS data revealed two distinct clusters at 62 allelic differences from each other. Seven of 229 food products tested positive for Salmonella Typhimurium. WGS analysis of the food isolates indicated matches with both clusters. Moreover, in December 2021, Salmonella isolates matching with the later identified clusters had also been found in samples during an own-check in the factory. Eleven types of products were recalled worldwide and food safety authorities shut down the factory 8 April 2022. A strong collaboration and information sharing between different stakeholders resulted in comprehensive measures to stop the spread of this international outbreak.

References

Joint ECDC-EFSA Rapid Outbreak Assessment  https://www.ecdc.europa.eu/sites/default/files/documents/1st-update-ROA_monophasic-S-Typhimurium-ST34_2022-00014_UK-amended-8-June.pdf [7]

RASFF 2022.1799 ; RASFF 2022.2201; RASFF 2022.2452