Rapid Outbreak Assessment: Multi-country outbreak of Salmonella Braenderup ST22, presumed to be linked to imported melons
Between 15 March and 6 July 2021, 348 confirmed S. Braenderup sequence type 22 (ST22) cases were reported in 12 European Union/European Economic Area (EU/EEA) countries and the United Kingdom (UK). The cases were spread throughout the countries and only two reported travel. A total of 68 cases were hospitalised. No deaths were reported.
The case interviews and an analytical epidemiological study suggested small melons (in particular Galia melons) as the possible vehicle of infection. S. Braenderup ST22 matching the outbreak strain was isolated in the UK in two imported Galia melons from one batch from Honduras, and in Austria from a pooled sample of melons (unknown origin) including Galia melons.
Based on epidemiological, microbiological and traceability investigations, the vehicles of infection are presumed to be melons imported from outside the EU/EEA and the UK. Galia melons from the batch imported from a Honduran producer are probable vehicles of infection, at least in those cases reporting having consumed Galia melons. Further investigation is needed to identify the point of contamination along the production chain.
The first cases in the EU/EEA and the UK were detected in March 2021, before the batch found to be contaminated had been harvested. This indicates that contaminated food vehicles had been circulating in these countries earlier. This is confirmed by the detection of the outbreak strain in melons in Austria in April 2021.
Control measures have been implemented for imported melons distributed on the EU market. The Honduran producer finished harvesting melons in April 2021. These melons are no longer on the market. No additional exports from Honduras are foreseen until the new season starts in December. These measures reduce the risk of new infections. Given delays in reporting and the possibility of secondary cases, further cases may still be reported, but with decreasing frequency.