Facts about E. coli

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Over the weekend a number of news sources have reported on an outbreak of E. coli infection in children in the UK. The outbreak has been linked to a children’s farm in Surrey and all the infected children are under 10 years old. According to BBC News, 36 cases have so far been reported._ The Times_ report focused on the number of children that the farm may have put at risk, estimating that this number may in the thousands because the farm was allowed to remain open for two weeks after it first "fell under suspicion".

This weekend a press release was issued by the Health Protection Agency (HPA), an independent organisation set up by the government to protect the public from health threats. It says that the farm is now closed to visitors while the HPA investigates the outbreak. Of the 36 children affected, 12 are reported to currently be in hospital with complications from their infection, with three children considered to be seriously ill.

What is E. coli?

Escherichia coli (E. coli) is a type of bacteria common in human and animal intestines, and forms part of the normal gut flora (the bacteria that exist in the bowel). There are a number of different types of E. coli and while the majority are harmless some can cause serious food poisoning and serious infection. For example, E. coli bacteria are a common cause of cystitis, an infection of the bladder that occurs when there is a spread of the bacteria from the gut to the urinary system. Women are more susceptible to urinary tract infection by E. coli because of the close proximity of the urethra and the anus.

Some types of E. coli can cause gastrointestinal infections. As the bacteria can survive outside of the body, its levels serve as a measure of general hygiene and faecal contamination of an environment. A common mode of infection is by eating food that is contaminated with the bacteria.

Some E. coli strains produce toxins (Shiga toxins) that can cause severe illness. One common strain called E. coli 0157 produces such toxins and is usually responsible for the outbreaks that are covered by the news. This strain is responsible for the outbreak linked to the farm in Surrey.

What are the symptoms of infection?

The symptoms depend on the site of infection and which type of E. coli is causing the infection. The children infected by the E. coli 0157 strain from the Surrey farm are likely to have had the classic symptoms linked to this strain, that include severe stomach cramps, vomiting, and diarrhoea that may be bloody. The symptoms usually last up to seven days if there are no complications, but some infections can be severe and may be life threatening.

A particular life-threatening complication called haemolytic uremic syndrome (HUS) may develop in 5-10% of people infected with a toxin-producing form of E. coli. This is a severe kidney-related complication that may, in extreme cases, lead to renal failure and the need for renal replacement therapy.

While all ages are at risk, the HPA explains that children may be more vulnerable to severe infections and complications because they cannot tolerate much fluid and blood loss through vomiting and diarrhoea.

How is E. coli treated?

The specific treatment will depend on the type of infection. Cystitis infections are usually self-limiting (they go away by themselves) after two to four days. In some cases a short course of antibiotics may be given.

Intestinal infections by E. coli are not usually treated with antibiotics either. Rehydration is important as a lot of fluid may be lost through diarrhoea. This is the mainstay of treatment and important whether the infection is being managed in hospital or at home. Oral rehydration solutions are particularly helpful in children with diarrhoea. In addition to providing fluids they also replace other important substances lost from the body, including sodium, potassium and glucose.

How can I prevent E. coli?

E. coli infections can be serious so preventing infections is important. The bacteria are usually spread through faecal matter reaching the mouth, so good hygiene is critical in preventing contamination and spread. This is particularly important with regards to going to the toilet or handling or preparing food as consumption of contaminated food or water and contact with infected faeces or animals are common sources of infection.

The usual hygiene rules apply, including the need to wash and dry hands thoroughly after going to the toilet and after touching animals (for example, at farms). Foods should be cooked thoroughly and it is best to avoid unpasteurised dairy products.

Some people have been infected by swallowing water while swimming or playing in lakes or ponds, and so the CDC recommends that swallowing water during these activities should be avoided.

How did these children become infected?

The precise details surrounding the outbreak of the E. coli infection at Godstone Farm in Surrey are currently being investigated. The HPA has published a timeline of the events leading up to the closure of the farm over the weekend.

The first laboratory case was confirmed on 27 August when Environmental Health Officers learned that an infected individual had visited the farm. A further two cases were confirmed around the 1 September. Environmental Health Officers and a Health Protection Agency team visited the farm on several occasions to inspect it and to advise on important hygiene messages.

Between 4 September and 11 September, the HPA received reports of further infections but all had been contracted prior to 3 September when a team inspected the farm and advised on more stringent hygiene measures and cessation of contact with high-risk animals. The HPA assumed that as the cases seem to have been infected before their advice, their control measures were working. On the 11 September, the HPA was informed of a further case arising from someone becoming infected on the 4 September. Based on this report the children's farm was closed on 12 September.

It is not clear precisely how the children were infected but it is likely to be related to petting the farm animals. Results of the investigation will reveal if this is the case.

While The Times focuses on the children that were put at risk by the delay between the first reported case and the farm closure, the HPA deem their response to be "proportionate and effective" for the scale of the incident up to and including 3 September. The farm is reported to be a busy farm, particularly during the school holidays, when it receives up to 2,000 visitors per day. Only 36 cases of infection have so far been reported.