Prolonged multi-country outbreak of Salmonella Strathcona ST2559 linked to consumption of tomatoes in the EU/EEA and the UK

Abstract

A cross-border outbreak of Salmonella Strathcona ST2559 is ongoing in the European Union/European Economic Area (EU/EEA) and the United Kingdom (UK). From 1 January 2023 to 5 November 2024, 232 confirmed cases of S. Strathcona ST2559 have been identified in 16 EU/EEA countries according to the European case definition: Austria (33), Croatia (3), Czechia (10), Denmark (9), Estonia (1), Germany (62), Finland (3), France (23), Ireland (1), Italy (67), Luxembourg (2), the Netherlands (2), Norway (3), Slovakia (5), Slovenia (2) and Sweden (6). Twenty-nine cases were also identified in the UK. Among the travel-associated cases, the most frequently visited country was Italy.

Tomatoes were identified as the vehicle of infection in several national epidemiological investigations undertaken in response to this multi-country outbreak. Whole genome sequencing cluster analyses suggest that the outbreak strain from multiple affected countries has a recent common origin.

The epidemiological, microbiological and traceability investigations in the 2023 Austrian outbreak and 2024 Italian outbreak confirmed that small tomatoes from the Sicily region of Italy were the vehicle of infection in these two outbreaks. The same conclusion was confirmed for a historical S. Strathcona ST2559 outbreak in Denmark in 2011.

Human and food sectors should continue to conduct investigations to verify whether small tomatoes from Sicily are the vehicle of infection in all EU countries that have reported or continue to report cases in this multi-country outbreak, as other foods could also be involved in the transmission. The environment's role in the contamination of the tomatoes should also be investigated, as the outbreak strain was also identified in a farm animal in the region. Investigations to identify the point of entry of S. Strathcona – including of irrigation water – should be conducted so the appropriate corrective measures are taken to stop the contamination from spreading and prevent possible new cases.