The bacteria produce a toxin that can be fatal An outbreak of E. coli linked to contaminated salad vegetables has caused at least 18 deaths and hundreds of infections in Germany, Sweden and other countries. What is E. coli? E. coli is short for Escherichia coli. It is a type of bacterium present in the gut of humans and other animals.
Most strains are harmless but some are able to produce toxins that can cause symptoms in humans.
The severity of the illness people can get varies considerably, but some types of E. coli lead to severe cramps and diarrhoea.
Previous outbreaks have been linked to the 0157 strain, however, this seems to be something different.
What do we know about this strain? Continue reading the main storyA new strain is one that is genetically different from other known strains and includes one or more pieces of DNA that have come from a different bacterium”End Quote Society for General Microbiology Initial tests looking for "markers" on the surface of the bacterium showed it to be the O104 strain, which the World Health Organization said was rare, had been seen in humans before, but never in an outbreak.
When researchers looked at all the genes inside the bacterium they concluded that it was in fact a new strain of O104.
Bacteria are able to exchange genes between different strains and species.
Experts believe this variant has acquired a deadly combination of producing a toxin which can damage the kidneys and being really good at sticking to the gut, allowing more bacteria to grow and ultimately produce even more toxin.
What are the health effects?Symptoms - such as diarrhoea with blood in it, severe cramps, and fevers, can take up to eight days to develop.
It is hoped that the number of cases will begin to fall following public health advice issued in Germany last week.
But the outbreak is causing severe infections and in a number of cases, affecting the blood and kidneys.
Haemolytic uraemic syndrome - an unusual complication of some types of E. coli as well as other infections - has been seen in hundreds of current cases.
This can be mild, however, in some cases it can lead to epileptic fits, permanent kidney failure and even death.
Large numbers of people between the age of 16 and 60 have developed haemolytic uraemic syndrome (HUS).
"It is extremely unusual for people in these ages groups to develop HUS," the Health Protection Agency says.
What is the health advice?The exact source of the contamination has not yet been determined.
Until the cause is known, German officials are telling people to avoid eating raw tomatoes, cucumbers and leafy salad including lettuce, especially in the north of the country, until further notice.
The UK's Health Protection Agency recommends travellers follow the same advice.
It says anyone returning from Germany with illness including bloody diarrhoea should seek urgent medical attention and mention their travel history.
Treatment will probably include fluids and pain killers. There is evidence that some common antibiotics might not work and some experts believe antibiotics could make the illness worse. For patients with severe HUS, dialysis might be needed to support failing kidneys.
Continue reading the main story Processed meats: hamburgers, kebabs and salamiCheese, milk, butter, yoghurt, ice cream and other dairy productsSalad vegetables such as coleslaw, lettuce, spinach, radishes and alfafa sproutsFruits including melons, grapes and apple juiceWaterborne outbreaks associated with lakes, ponds, paddling and swimming poolsThe Food Standards Agency in the UK has issued general advice on the need to wash fruit and vegetables.The agency says: "It's a good idea to wash fruit and vegetables before you eat them to ensure that they are clean, and to help remove germs that might be on the outside.
"Peeling or cooking fruit and vegetables can also remove these germs."
However, a Scottish expert said new research suggests washing alone may not be enough, as the bacteria may be inside the food.
Dr Nicola Holden of The James Hutton Institute said: "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."
She said the bacteria can colonise plant roots, moving up to the edible foliage or fruits.
"The threat to human health occurs because these bacteria are not simply sitting on the surface of the plant and are particularly difficult to remove post-harvest," she added.
What do other experts say?Professor Brendan Wren from the London School of Hygiene & Tropical Medicine said E. coli can attach to the surface of fresh produce such as lettuce leaves, spinach leaves and cucumber.
"These types of E.coli survive harsher environmental conditions than the typical E. coli and produce some nasty toxins to humans," he said.
"They can survive in soil environments and fertiliser may be one source for the origin of the outbreak related to fresh produce such as cucumbers."
Dr Jonathan Fletcher, senior lecturer in microbiology at the University of Bradford, said toxin-producing E. coli can cause very serious disease in humans, especially in the elderly or very young.
Cattle seem to carry the toxin in their gut, without showing signs of illness, and it will be shed in the faeces.
"If cattle manure is used as a fertiliser, it is probable that vegetables such as cucumbers will be contaminated with E. coli, and if not washed properly it would be present in sufficient numbers to cause the infection."
Where has it come from?The source of this outbreak is believed to be contaminated salad vegetables.
Initial reports that cucumbers were the source of the bacteria have not been confirmed and other food sources are being sampled.
While E. coli infection is often caused by eating undercooked meat and eggs, there has been a recent rise in cases caused by fresh fruit and vegetables.
They include foods that are eaten raw or only lightly cooked, such as salads, fresh fruit and bean sprouts.
A whole host of foods have been linked with past E. coli outbreaks.
What about the UK?The total number of cases in the UK is seven.
That includes three British nationals and four Germans. It seems all picked up the infection in Germany.
Three have developed the potentially deadly complication of haemolytic uraemic syndrome.
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