Public Health England has issued an update on its investigation into an outbreak of E. coli O157 infection that affected at least 19 people in the UK in September 2013. The outbreak was linked to consumption of pre-packed watercress purchased from Sainsbury’s supermarkets.
The retailer recalled the implicated watercress immediately when the link was established, but according to the investigation update a further related case was reported in October after restocking. The source of the contamination that led to the outbreak has never been confirmed, despite extensive microbiological testing of product and environmental samples taken at farms supplying watercress to Sainsbury’s.
However, the investigation did uncover a second, smaller, outbreak of six cases of E. coli O157 infection caused by a different strain of the pathogen. This too was linked to watercress from Sainsbury’s, but on this occasion the investigation was able to isolate the outbreak strain from a watercress bed at a farm supplying the supermarket. This bed was found to be close to a field containing cattle, leading to the conclusion that the contamination probably occurred as a result of water run-off or from wildlife moving from the filed to the watercress farm.
More information can be found here.