Disturbing reason for surge in lettuce-related food poisoning bug linked to bowel cancer explosion in under 50s
Officials this week sounded the alarm over a surge of serious cases of a diarrhoea-causing bacterial infection that's been linked to colon cancer.
Rates of a rare strain of the bug E.coli, found commonly in contaminated lettuce, have risen almost 10-fold in England in just seven years.
Cases of the infection are thought to be linked to the mysterious epidemic of colon cancer among the under 50s.
Now, experts have told of the potential reasons behind the E.coli explosion — including climate change, more vigilant reporting by hospitals and a rise in the number of people vulnerable to severe illness.
It may also be the case that more shoppers are opting for prime sources of the bug, such as lettuce, either via ready made sandwiches or bagged salads.
Studies suggest leafy greens are responsible for half of all E.coli outbreaks.
Experts believe lettuce's texture can make it more prone to the bacteria and fact it's not cooked, which would usually kill off bugs, increases the risk.
Professor Paul Hunter, a renowned infectious diseases expert from the University of East Anglia, told MailOnline: 'Watering during growth allows the potentially contaminated water to rest on the lettuce leaf.
Last year, more than 280 people were struck down by STEC in an outbreak linked to ready meal sandwiches containing contaminated lettuce grown in the UK
Last year, more than 280 people were struck by the harmful strain, called STEC, in an outbreak linked to ready meal sandwiches containing contaminated lettuce grown in the UK.
'The rough and waxy surface of the leaf also makes it difficult to wash off E. coli,' Professor Hunter added.
'The main risk comes from bacteria attached to the leaf surface. Most other vegetables are either peeled or cooked before eating.
'Things like cucumbers, tomatoes and peppers may not be cooked but grow some way off the ground so less likely to be contaminated.'
A 2019 review of research co-authored by Professor Hunter also analysed 35 STEC outbreaks linked to lettuce between 1995 and 2018.
Eight were found to have 'poor practice' such as insufficient disinfection when processing of the vegetables, which 'may have contributed to the outbreak'.
A further six were linked to animal faeces near the growing fields.
'Where the type of lettuce was reported, it was usually Cos lettuce, though Iceberg and Mesclun lettuce were each implicated in one', Professor Hunter said.
Symptoms of Shiga toxin-producing E.coli include severe diarrhoea and vomiting, according to the UK Health Security Agency
'We also found bagged lettuce already prepared for use to be a common factor.'
But experts also warn that warm, wet weather — increasingly common due to climate change — can create an 'ideal' breeding ground for STEC to spread.
A report released by the UK Health Security Agency (UKHSA) earlier this week blamed a combination of 'high rainfall' and warm temperatures for a STEC outbreak affecting more than 250 adults in summer of 2022.
The 'majority' of cases had consumed iceberg lettuce, officials said.
'Prolonged periods of heat', including temperatures of 40 degrees Celsius 'followed by high rainfall' likely caused contaminated soil to be mixed with water and spread over crops, they added.
Experts also warned last year that people could be at especially high risk of contracting the bug due to unusually high levels of rainfall.
Professor Eileen Wall, head of research at Scotland's Rural College (SRUC), a research institution focused on agriculture and life sciences, said: 'Rain can cause contaminated water to splash onto the leaves of the lettuce, while warmth provides a favourable temperature for bacterial proliferation.'
Bacteria could spread to lettuce through irrigation water — particularly if the water is contaminated with faecal matter, she added.
Another factor likely to be involved in the rise is the increase in surgical procedures on patients who need catheters, which are known to be an infection hotspot.
E.coli can also be contracted via the urinary tract; where bacteria from the bladder enters the bloodstream via the genitals.
Professor Hunter said: 'If you're older you are more likely to have a urinary catheter which is a big risk factor.
'Equally, as you get older, you can get more problems with the bowel that could ultimately lead to bacteria entering the blood.'
It may also simply be the case that the UK has adopted a more vigorous method of reporting E.coli cases.
The official figures include patients who become so ill with the infection they seek help at a GP clinic or hospital. It means a rise in cases could also mean more Britons are in poorer health, and more likely to become very sick with E.coli.
Official data published in August last year showed that severe E. coli cases have surged by more than 4,000 in a single year — the biggest annual rise in four years.
A MailOnline analysis of the data revealed that severe E. coli infections are up roughly 10 percent on the previous year, amounting to more than 46,000 cases in England between June 2023 and June 2024.
Rates of a rare strain of the bug E.coli — known as non-0157 shiga toxin-producing E.coli (STEC) — have risen almost 10-fold in England in just seven years
The previous three years saw much smaller rises of around just four per cent.
It comes as concerning research this week suggested E.coli may be to blame for a disturbing rise in colon cancer cases in under 50s, a phenomenon that has baffled doctors around the globe.
US researchers analysed the DNA of 981 colon cancer tumours in patients aged either under 40 or over 70, across 11 countries.
They found traces of colibactin, a cancer-linked toxin produced by certain strains of E. Coli, lurking in tumors from patients under 40.
Limited research has also previously shown that the toxin colibactin is produced by some non-O157 STEC strains.
STEC is considered to be extremely infectious, and in up to 15 per cent of cases, the bug can cause haemolytic uremic syndrome (HUS), a life-threatening condition that can lead to kidney failure.
Children under the age of five are at the highest risk of HUS.
A small proportion of adults may develop a similar condition called thrombotic thrombocytopaenic purpura (TTP).
