Where is E. coli found?

• Food which comes into contact with manure
• Petting farms
• Contaminated water

STEC is regularly found in the lower intestine of animals, especially cows, but also sheep and goats, and doesn’t cause them any problems, says McNally.

However, if manure from these animals infiltrates food, it can cause infections in people.

This contamination can occur due to food, such as meat or dairy products, coming into direct contact with animal faeces during the slaughter process. If this meat is then raw or undercooked when people eat it, they are likely to become unwell, says McCarthy.

Alternatively, if manure gets into the water supplies for farms, which is then used to water leafy greens and vegetables, people can become infected, he explains.

When STEC O157 was identified in the late 1990s at a butcher’s shop in Wishaw, Scotland – in one of the world’s worst outbreaks to date – it was associated with poor hygiene from handling raw food, says McNally. 

“Then we got a lot of cases from petting farms, which is why they are now quite strict with hygiene measures there,” he says.

“Now what we’re seeing more and more is outbreaks associated with pre-packed salads and processed foods – basically anything where the food isn’t cooked but is pre-packed, processed and nationally distributed.” 

For example, an outbreak in Germany in 2011, that infected thousands and killed dozens, was traced back to bean sprouts. “Outbreaks tend to be big because it’s very difficult to identify the foodstuff that’s been contaminated,” says McNally.

Drinking contaminated water from lakes, rivers or taps can also cause a STEC infection, says McCarthy. Swimming in pools or the sea can also pose an infection risk but this is less common, he says. “To minimise the risk, it is important that you do not swim in dirty water or swallow the water,” he adds.

Is E. coli contagious? How does it spread?

When it comes to transmission, “people shouldn’t fear that they’re going to get this from the person sitting next to them – it’s not like Covid, that’s not how they spread,” says McNally.

However, it can spread between people through the faecal-oral route of transmission. This occurs if an infected person does not correctly wash their hands after using the lavatory and handles another person’s food.

The UKHSA warns that the bacteria can spread within families and in nurseries, schools, care homes and hospitals.

How can you prevent it?

• Regularly wash your hands with warm water and soap (alcohol gels do not kill all bugs)
• Wash fruit and vegetables and cook food properly
• Do not prepare food for others if suffering from diarrhoea and vomiting
• Don’t return to work, school or nursery until 48 hours after symptoms have stopped
• Use disinfectants to clean surfaces

Tens of thousands of foods vulnerable to E. coli contamination are distributed across the country every week and only a handful of people become unwell, so a person would be unlucky to become infected, says McNally.

However, there are some steps people can take to reduce their risk of consuming the bacteria. 

“In our house, we always wash every bit of fruit and veg before it’s consumed,” says McNally. “If you’re buying a pre-packed salad from a shop, there’s a benefit to washing it.”

He also recommends being “very cautious” about consuming unpasteurised dairy products and raw milk (which haven’t been treated to kill harmful bacteria). “There is always the possibility of some faecal contamination of those dairy products as they’re made.”

How can you treat it?

“If you see blood in your stool, then you should be contacting the doctor because it’s important that as many cases as possible are notified to the UKHSA,” says McNally.

However, while diarrhoea is unpleasant, it is self-limiting, so should pass on its own without treatment, he says. 

There is no specific treatment for a STEC infection but it’s important to drink plenty of fluids as diarrhoea can lead to dehydration, says the UKHSA. The NHS advises drinking small sips of water often and eating solid foods as soon as you feel able to, while pharmacists may also recommend using rehydration powders.

If a STEC infection lasts for more than a week, then go back to the doctor. “Treatment options are tricky because STEC produces toxins when they come under stress, such as when exposed to antibiotics,” McNally says.

As a result, doctors don’t typically prescribe antibiotics and would favour letting the illness run its course, unless it is a very serious case.