A multi-country outbreak of Salmonella Blockley associated with tomato consumption, July to October 2024

Between July and October 2024, 216 cases with genetically related Salmonella Blockley sequence type 52 were identified in France (n = 56), Germany (n = 30), the United Kingdom (UK) (n = 129) and the United States (US) (n = 1). Case interviews in the UK identified tomatoes as a possible vehicle of infection. A rapid case-control study with 29 cases and 87 controls was conducted to investigate this hypothesis, using pre-existing control data. Multivariable, Firth penalised logistic regression was used to explore associations between illness, food exposures and retailers. Consumption of tomatoes and shopping at Retailer A (adjusted odds ratio (aOR) = 10.75; 95% confidence interval (CI): 1.52-103.16) was associated with being a case. Salmonella spp. was not detected in any of the 312 tomato samples tested by a standard culture method, but a low concentration of Salmonella DNA was detected in two enriched broths by PCR. These detections could not be confirmed by culture. Evidence derived from epidemiological, microbiological and food chain investigations in the UK identified imported tomatoes from Morocco as the most likely vehicle of infection.