The UK Health Security Agency (UKHSA) has published a report on
a multi-agency
investigation into the UK's largest ever Shiga toxin-producing
Escherichia coli (STEC) O145 outbreak.
STEC are bacteria which can cause severe food poisoning. People
with STEC food poisoning can develop symptoms such as diarrhoea,
stomach cramps, vomiting and fever.
The outbreak involved 293 cases between May and November 2024.
Almost half of these were admitted to hospital with 11 cases
developing complications such as Haemolytic Uraemic Syndrome (a
condition which causes kidney failure). There were 2 reported
deaths.
In May 2024 UKHSA, Public Health Wales (PHW) and Public Health Scotland
(PHS) identified a
rapid rise in STEC cases detected through routine disease
surveillance.
Whole genome sequencing (WGS) helped experts at UKHSA,
PHW and PHSto link affected cases,
revealing the scale of the large national outbreak.
UKHSA led the investigation, working with agencies across the 4
UK nations to rapidly identify the cause. This included speaking
to people about what they had eaten before becoming unwell and
using this information to carry out scientific studies.
Pre-packaged sandwiches containing lettuce were identified as the
likely cause of the outbreak.
The Food Standards Agency (FSA) and Food Standards Scotland
(FSS) coordinated rapid investigations with local authorities and
industry partners to trace back and analyse the food chain
information provided by cases. This analysis identified 3 common
sandwich manufacturers, and UK-grown Apollo lettuce was
identified as the likely contaminated ingredient. As a result,
the 3 manufacturers undertook a precautionary voluntary recall.
Amy , Lead Epidemiologist at UKHSA said:
This outbreak demonstrates the vital importance of UK government
agencies working together with industry to take decisive action
to protect people's health.
It also highlights the crucial role that whole genome sequencing
continues to play in disease surveillance, helping us to detect
and stop outbreaks more quickly than ever before.
Outbreaks involving fresh produce or ready-to-eat foods are
particularly challenging to investigate due to the speed with
which they emerge and the high number of cases that we must
assess.
By the time we are made aware of an outbreak, often none of the
implicated food products are available for testing because they
have either been eaten or disposed of, making it difficult to
confirm whether they were contaminated.
STEC O145 is a growing threat which is now one of the most common
types of Shiga toxin-producing E. coli that we are detecting in
our surveillance.
Jacquelyn McCormick, Head of Incidents at the FSA said:
Close collaboration between UK public health and food safety
authorities supported by industry partners and local authorities
enabled us to quickly investigate and identify the source of the
outbreak.
This outbreak demonstrates the complexity of the supply chain and
how critical it is for government organisations and the food
industry to work together to respond rapidly to food safety
concerns and protect public health. The learnings from this are
being used to continually improve supply chain controls to ensure
food is safe.
Despite extensive investigation it was not possible to confirm
how the lettuce had become contaminated.
