ONE of the UK's largest ever E.coli outbreaks, which saw 259 people fall ill and 75 hospitalised, was linked to salad leaves, a new report has revealed.
The cases were traced back to one unnamed salad grower who supplied the salad to national chains and retailers across Britain.
Escherichia coli O157, sometimes called STEC (Shiga toxin-producing Escherichia coli) isa type of that can cause severe .
The name O157 refers to a specific type of outer cell membrane protein, and the fact that it produces Shiga toxins, which damage the lining of the intestines.
It's caused byconsuming food or water contaminated with the , particularly undercooked meat, unpasteurised milk, or contaminated produce.
In , around 800-1000 cases are reported annually.
The 2022 outbreak saw 259 confirmed cases of the E.coli strain – had 195 cases, had 33, Northern had 18 and had 13.
While 75 people were reported to be hospitalised, no patients were diagnosed with hemolytic uremic syndrome (a serious condition that can develop and lead to ), and no deaths were recorded.
Initial investigations pointed to the consumption of foods from national fast-food chains and having salads and chicken products.
The Food Standards Agency (FSA), which analysed food exposure information and traceability investigations identified linked supply chains of UK grown fresh produce.
The single unnamed salad grower was then linked to other identified growers and processors in the supply chain, and to and retailers the cases had visited.
Salad leaves, such as lettuce, spinach, baby leaf spinach, cos romaine and other leaf types were linked to the majority of cases interviewed – there was no strong link to one specific type of leafy green.
Investigations by the FSA revealed growers and suppliers had noted prolonged periods of extremely dry , followed by a lot of rain in July and August 2022 – which in some cases caused flooding.
Heavy rainfall washing pathogens from animal pastures into fields with crops, contaminating the water supply, could have played a role, said the UK Health Security Agency (UKHSA).
At the time, the source or cause of the outbreak couldn't be established, and it was essentially over by the time links to the specific salad supply chains had been established.
There were also no items to sample to confirm the findings microbiologically.
Supply had also switched to imported products so no ongoing risk was identified.
According to the report: “Although case numbers had reduced by the time the most likely implicated food supply chain had been identified, a re-emergence of the outbreak strain is possible in future years.
“Owing to the resumption of domestically produced salad in the next season, re-contamination of fresh produce due to persistence of the organism within the environment, which may explain the cases spanning multiple years in this cluster, is possible.”
Six recommendations were made, including that the UKHSA should review surveillance to monitor and track infections.
Also, improvements where gaps were identified to enhance the detection and risk assessment of emerging outbreak clusters.
