2 Jun 2011

Q and A: What is E.coli?

How dangerous is it? How is it caught? Can it be destroyed? Channel 4 News answers your questions on E.coli as experts say the current outbreak has been caused by a toxic mutated strain.

Q and A: What is E.coli?

What is E.coli?
Escherichia coli (E.coli) is a bacterium commonly found in the gut of humans and warm-blooded animals. Most strains are harmless but some, such as enterohemorrhagic E. coli (EHEC), can cause serious illness.

Why are people catching E.coli?
E.coli is transmitted to humans mostly through foodstuffs, including raw or undercooked ground meat products and milk. Examples of foods involved in previous E.coli outbreaks include undercooked hamburgers, dried cured salami, unpasteurised fresh-pressed apple cider, yoghurt, cheese and milk.

Faecal contamination of water and other foods, as well as cross-contamination during food preparation (with beef and other meat products, contaminated surfaces and kitchen utensils), will also lead to infection.

An increasing number of outbreaks have been linked with eating fruit and vegetables (such as sprouts, lettuce, coleslaw and salad). In these cases, contamination occurs due to contact with animal faeces.

Can people pass on the infection?
Yes, the infection can be transmitted from person-to-person through the oral-faecal route. At the time of writing, all of the cases but two involved in the current outbreak are people who have recently visited northern Germany, or had contact with a visitor from northern Germany.

Visiting farms and places where people might come into direct contact with farm animals has also been identified as a risk factor for EHEC infection.

Can the bacteria be destroyed?
EHEC is destroyed by cooking foods thoroughly to a temperature of 70C or higher.

What is the latest strain?
Scientists are still trying to work out exactly which strain of E.coli is causing such devastating consequences in humans. Researchers in China have said preliminary genetic analysis of the outbreak suggests the bacterium is unique. They point to genes from two distinct groups of E. coli: enteroaggregative E. coli (EAEC) and EHEC.

Hilde Kruse, a food safety expert at the World Health Organisation (WHO), has said: “This is a unique strain that has never been isolated from patients before.”

Q and A: What is E.coli?

What are the symptoms of E.coli?
Symptoms of EHEC include abdominal cramps and diarrhoea that may be bloody. People may also experience fever and vomiting. Many of the victims who have been identified so far have these symptoms.

The incubation period for EHEC can range from three to eight days, but is typically three to four days. Most patients recover within 10 days, but a small number will go on to develop haemolytic uraemic syndrome (HUS).

People with HUS suffer acute renal failure and, in some cases, damage to the central nervous system. It is estimated that up to 10 per cent of patients with EHEC infection may develop HUS, with 3 per cent to 5 per cent dying as a result.

It is possible to pass EHEC to other people, which is why health experts urge good hygiene.

What health advice is being given?
All the people in the UK affected by the outbreak have travelled to Germany. The Health Protection Agency says people travelling to Germany should avoid eating raw tomatoes, cucumbers and leafy salad including lettuce, especially in the north of the country.

Anyone returning to the UK from Germany who feels unwell, including having bloody diarrhoea, should seek urgent medical help.

The Food Standards Agency in the UK has issued general advice on the need to wash fruit and vegetables. Peeling or cooking fruit and vegetables may also remove germs.

However Dr Nicola Holden, of the James Hutton Institute, said washing may not be enough.

She said the outbreak could be an indication that fruit and vegetables are ingesting these bacteria as they grow.

“The bacteria are able to get from animal sources on to crops through different routes, most likely in irrigation water or sometimes from slurry spraying, while some contamination can also occur during processing and packaging.”

Source: WHO