Key facts
- Between 1 January 2023 and 5 November 2024, 232 cases of Salmonella Strathcona have been reported in 16 EU/EEA countries and three countries outside the EU/EEA (the United Kingdom, the United States, and Canada).
- Investigations revealed that isolates from cases that are genetically closely related to the outbreak strain have been detected since 2011.
- Based on epidemiological, microbiological and traceability investigations, small tomatoes from the Sicily region of Italy were identified as the vehicle of infection.
- The risk for new infections remains as long as the seasonal deliveries of contaminated produce continue.
Overview
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). Cases were also identified in three countries outside the EU/EEA; the UK (29), the US (8) and Canada (5). 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.
ECDC assessment
This is a re-emerging, seasonal outbreak where 232 S. Strathcona infections have been reported by 16 EU/EEA countries, the UK, and the US since January 2023, with most cases reported between the months of August and October. Epidemiological, microbiological and traceability investigations identified small tomatoes grown in the Sicily region of Italy as the vehicle of infection.
The risk for new infections remains as long as the seasonal deliveries of contaminated produce continues. New outbreaks are likely to occur in future seasons until the root cause of the contamination has been identified and control measures implemented. Human and food sectors are recommended to continue investigations to verify whether small tomatoes from Italy are the vehicle of infection in newly occurring cases. The role of the environment, including irrigation water in the contamination of the tomatoes should also be investigated, to identify the point of entry at which contamination with S. Strathcona is occurring.