Common source, common food vehicle: investigations of recurring Salmonella Strathcona outbreaks in Europe since 2011

In 2011, a rare type of Salmonella was reported for the first time in Europe connected to an outbreak in several European countries. At the time, outbreak investigations pointed at small tomatoes from Sicily (Italy) as the likely source for the salmonellosis cases caused by Salmonella Strathcona.

Since then, Salmonella Strathcona notifications in Europe have shown a recurring seasonal outbreak pattern usually from summer to the beginning of the following year. In a ‘Euroroundup’ published in the journal Eurosuveillance, Brait et al. describe the epidemiology of cases between 2011 and 2024, explore the genomic relatedness of the detected subspecies and try to identify the possible food vehicle for the recent outbreaks. [1]

During the study period, the authors identified 662 S. Strathcona infections across 17 countries: 469 confirmed, 161 probable, 13 possible and 19 non-outbreak cases. Almost half (306) of the 643 outbreak cases were reported during an outbreak between 2023–2024. Germany notified the largest number of outbreak cases (n = 229; 36%), followed by Denmark (93) and Austria (77).

Not all countries that observed Salmonella Strathcona cases since 2011 joined the collaborative investigation for this study and since case identification was largely based on mandatory notification, the authors hypothesise that the true number of infections is likely substantially higher. In addition to the identified cases until 2024, a further 29 cases have been reported during 2025 (until beginning of September 2025).

Common source and common food vehicle

Whole genome sequencing of isolates during the study period showed that almost all (95%) were highly genetically related over time and across countries, compatible with a common source.

Brait et al. “deem it likely that tomatoes may have been the vehicle in most if not all the years”. In 2011, Denmark had observed most of the cases in the first European S. Strathcona outbreak and investigations had identified small tomatoes from Sicily as the vehicle of the infection. 

Previous Salmonella outbreaks e.g. in Sweden, Finland and the United States have established fresh tomatoes as food item vehicle. This can be related to consumption of tomatoes without cooking or the fact that pathogens may be part of the plant tissues – which could mean that washing of tomatoes may not be an effective preventive measure against salmonellosis.

According to Brait et al., their investigations “suggest recurring outbreaks in Europe since 2011 with a seasonal pattern of S. Strathcona cases that are linked to small tomatoes originating from a common source. The investigation exemplifies the added value but also the need of extensive collaborative cross-border and cross-sectoral investigations, ideally supported by ECDC and EFSA, to address complex food-borne outbreaks”.

[A Rapid Outbreak Assessment on the 2025 outbreak is forthcoming.]

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Notes to editors/reference

[1] Brait Vivien, Böff Lena, Zmarlak-Feher Natalia Marta, Jourdan-Da Silva Nathalie, Mazzilli Sara, Pardos de la Gandara Maria, Moura Alexandra, Mossong Joel, Ernst Corinna, Ragimbeau Catherine, Pijnacker Roan, Lanzl Maren, Brandal Lin T, Lange Heidi, Stephan Roger, Biggel Michael, Raess Michelle, Daniel Ondřej, Spačková Michaela, Clarke Christina, Cormican Martin, Colgan Aoife, Garvey Patricia, Mckeown Paul, Dryselius Rikard, Karamehmedovic Nadja, Grilc Eva, Trkov Marija, Pirš Mateja, Brown Derek, Browning Lynda, Hoban Ann, Godbole Gauri, Painset Anais, Chattaway Marie Anne, Vainio Anni, Rimhanen-Finne Ruska, Fischer Jennie, Lamparter Marina C, Mattheus Wesley, Commans Florian, Grginić Ana Gverić, Mlinarić Ivan, Pem-Novosel Iva, Kurečić Filipović Sanja, Ferencak Ivana, Jurić Dragan, Niskanen Taina, Jernberg Cecilia, Rizzi Valentina, Sarno Eleonora, Kornschober Christian, Wolfsbauer Andreas, Werber Dirk, Simon Sandra, Gymoese Pernille, Ethelberg Steen, Müller Luise, Maritschnik Sabine, Meinen Anika, Pietsch Michael. Insights into recurring multi-country outbreaks of Salmonella Strathcona associated with tomatoes, Europe, 2011 to 2024. Euro Surveill. 2025;30(41):pii=2500224. Available from: https://doi.org/10.2807/1560-7917.ES.2025.30.41.2500224

[2] In 2023, non-typhoidal salmonellosis was the second most frequently reported gastrointestinal infection among humans in the European Union and European Economic Area (EU/EEA) countries after campylobacteriosis, accounting for 78,307 cases reported by 30 EU/EEA countries with an incidence of 18.15 cases per 100,000 population [See ECDC Surveillance Atlas of Infectious Diseases]. Notification of non-typhoidal salmonellosis is mandatory in 27 EU/EEA countries, while it is voluntary in Belgium, France and the Netherlands.