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E. coli O157 national outbreak update

Information on the national outbreak of E. coli O157 which has now been declared over.

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Latest update

Public Health England (PHE) has been investigating a national outbreak of a rare strain of E. coli O157 that was identified by PHE’s whole genome sequencing (WGS) technology. There have been 161 cases of this strain of E. coli identified (England 154, Wales 6 and Scotland 1). As the latest date of onset in a primary case is 5 July, this outbreak has now been declared over.

Investigations were undertaken by PHE’s epidemiological and microbiological staff working with the Food Standards Agency (FSA) and Local Authority Environmental Health staff. Epidemiological investigations identified mixed salad leaves as the likely cause of the outbreak.

Professor Jeremy Hawker, Incident director at PHE, said:

We are pleased to confirm there have been no new primary cases identified. This is a very strong indication that the outbreak is over. We continue to work closely with the FSA to confirm the source of this outbreak and to take all the appropriate measures to protect the public.

We urge people to remove any loose soil before storing vegetables and thoroughly wash all vegetables and salads that will be eaten raw unless they have been pre-prepared and are labelled ‘ready to eat’. These measures may reduce the risk of infection from any E. coli contaminated vegetables and salad but will not eliminate any risk of infection completely.

Richard Hoskin, Head of Incidents at the FSA, said:

Consumer protection has been the main priority throughout this investigation and we are pleased that the outbreak appears to be over. We are continuing to work hard to identify the source of the outbreak and obtain the necessary assurances from industry that appropriate hygiene controls are in place. We also encourage people, as a precaution, to follow our food hygiene advice to minimise the risk of illness.

E. coli O157 infection can cause a range of symptoms, from mild diarrhoea to bloody diarrhoea with severe abdominal pain. On rare occasions, it can also cause more serious medical conditions and can be caught by eating contaminated food or by direct contact with animals with the bacteria. It can also be passed from an infected individual to another person if hand and toilet hygiene is poor.

Read more information about E. coli O157 and hygiene advice on NHS Choices.

Previous updates

28 July

PHE is continuing to investigate the previously reported outbreak of E. coli O157. These investigations suggest there to be a strong association with eating mixed salad leaves.

PHE now confirms there have been no further cases identified since the previous update on 21 July. The number of cases remains at 161 (England 154, Wales 6 and Scotland 1).

Dr Isabel Oliver, Director of PHE’s field epidemiology service, said:

We are very pleased to see there have been no further cases reported over the past week, which suggests we are over the worst for this outbreak.

As previously, we strongly advise maintaining good hand and food hygiene practices at all times, particularly for anyone affected in order to stop the infection passing to others. It remains vital to wash hands thoroughly using soap and water after using the toilet, before and after handling food and after contact with any animals and pets, including farm animals. Small children should also be supervised when washing their hands.

It is important to remove any loose soil before storing vegetables and to thoroughly wash all vegetables (including salads) that will be eaten raw unless they have been pre-prepared and are specifically labelled ‘ready to eat’. These measures may reduce the risk of infection from any E. coli contaminated vegetables, fruit and salad but will not eliminate risk of infection completely.

Our investigations to identify the source of the contaminated salad leaves are continuing.

PHE continue to work alongside the FSA and will continue to provide any further necessary public health advice as investigations continue.

21 July 2016

Public Health England (PHE) is continuing to investigate an outbreak of E. coli O157, which is associated with eating mixed salad leaves. Latest figures suggest that the outbreak is now subsiding, but the outbreak control team remain vigilant to further cases and the risk of those affected passing the infections to others. Work continues with partners, including the FSA, to investigate the source.

Following the last update on 14 July, PHE can now confirm that 160 cases of this strain of E. coli have been identified (figure correct as at 21 July 2016). This is 153 in England, 6 in Wales and 1 in Scotland.

Dr Isabel Oliver, director of PHE’s field epidemiology service, said:

We are pleased to see a very significant reduction in the number of cases with 9 reported over the past week. This could indicate that we are over the worst of this outbreak, with those affected reporting the last onset of symptoms on 5 July. But this is still too many, and the risk of those affected passing the infection onto others remains. Strict hygiene measures are essential for anyone affected, to stop the infection passing to others. It’s vital to wash hands thoroughly using soap and water after using the toilet, before and after handling food and after contact with any animals and pets, including farm animals. Small children should also be supervised when washing their hands.

We also continue to stress the importance of good hand and food hygiene practices at all times. We urge people to remove any loose soil before storing vegetables and thoroughly wash all vegetables (including salads) that will be eaten raw unless they have been pre-prepared and are specifically labelled ‘ready to eat’. These measures may reduce the risk of infection from any E. coli contaminated vegetables, fruit and salad but will not eliminate any risk of infection completely. PHE is working alongside the FSA and will provide any further necessary public health advice as investigations continue.

PHE is using various approaches including whole genome sequencing (WGS) technologies to test samples from those affected. WGS technologies are at the forefront of improving the diagnosis of infectious diseases and this testing has indicated that the strain involved is likely to be an imported strain, possibly from the Mediterranean area.

Dr Oliver added:

Our investigations to identify the source continue to show that several of the affected individuals ate mixed salad leaves including rocket leaves prior to becoming unwell. The source of the outbreak remains unconfirmed and under investigation; we are not ruling out other food items. It’s important to be aware that no individual wholesaler, supplier, retailer, or restaurant has been confirmed as the source and currently the Food Standard Agency’s investigations focus on the distribution of mixed salad leaves to wholesale and not supermarkets.

PHE is also working closely with the FSA to trace, sample and test salad products grown in the UK and other parts of Europe. All food sample results to date have been negative for E. coli O157, but it’s important to be aware that where food has been contaminated with E. coli O157, it is not always possible to identify the bacteria on food testing.

A small number of wholesalers continue to be advised to cease adding some non-UK salad leaves to their mixed salad products pending further investigations.

14 July 2016

Public Health England (PHE) is continuing to investigate an outbreak of E. coli O157, which appears to be associated with eating mixed salad leaves.

Following the last update on 5 July, PHE can now confirm that 151 cases of this strain of E. coli have been identified (figure correct as at 13 July 2016). This is 144 in England, 6 in Wales and 1 in Scotland, with the South West of England particularly affected. 62 of the cases are known to have received hospital care and sadly, 2 of the individuals with E. coli O157 infection have died.

Dr Isabel Oliver, director of PHE’s field epidemiology service, said:

PHE has been working to establish the cause of the outbreak and has identified that several of the affected individuals ate mixed salad leaves including rocket leaves prior to becoming unwell. Currently, the source of the outbreak is not confirmed and remains under investigation; we are not ruling out other food items as a potential source.

PHE is using various approaches including whole genome sequencing (WGS) technologies to test samples from those affected. WGS technologies are at the forefront of improving the diagnosis of infectious diseases and this testing has indicated that the strain involved is likely to be an imported strain, possibly from the Mediterranean area.

PHE is also working closely with the FSA to trace, sample and test salad products grown in the UK and other parts of Europe. All food sample results to date have been negative for E. coli O157, but it’s important to be aware that where food has been contaminated with E. coli O157, it is not always possible to identify the bacteria on food testing.

As an additional precautionary measure, we have advised a small number of wholesalers to cease adding some imported rocket leaves to their mixed salad products pending further investigations.

5 July 2016

PHE is continuing to investigate an outbreak of E. coli O157, which may be associated with eating mixed salad leaves. To date, 109 cases (figure correct as at 4 July 2016) of this strain of E. coli have been identified (102 in England, 6 in Wales and 1 in Scotland) with the South West of England particularly affected.

PHE has been working to establish the cause of the outbreak and has now identified that several of the affected individuals ate mixed salad leaves including rocket leaves prior to becoming unwell. Currently, the source of the outbreak is not confirmed and remains under investigation. PHE is now reminding people to maintain good hygiene and food preparation practices in response to the current outbreak.

E. coli O157 infection can cause a range of symptoms, from mild diarrhoea to bloody diarrhoea with severe abdominal pain. On rare occasions, it can also cause more serious medical conditions and can be caught by eating contaminated food or by direct contact with animals with the bacteria. It can also be passed from an infected individual to another person if hand and toilet hygiene is poor.

Dr Isabel Oliver, director of PHE’s field epidemiology service, said:

PHE has put in place heightened surveillance for this strain of E. coli and is carefully monitoring the reporting of cases across the entire country. To assist with this investigation to help us find the source, we have convened a national outbreak control team who will also ensure all necessary control measures are put in place.

Currently, the source of the outbreak is not confirmed and this remains under investigation. However, our preliminary investigations have indicated that several of the affected individuals ate salad items including rocket prior to becoming unwell. At this stage we are not ruling out other food items as a potential source.

We continue to stress the importance of good hand and food hygiene practices at all times. We urge people to remove any loose soil before storing vegetables and thoroughly wash all vegetables (including salads) that will be eaten raw unless they have been pre-prepared and are specifically labelled ‘ready to eat’. These measures may reduce the risk of infection from any E. coli contaminated vegetables, fruit and salad but will not eliminate any risk of infection completely. PHE is working alongside the FSA and will provide any further necessary public health advice as investigations continue.

It’s also vital to wash hands thoroughly using soap and water after using the toilet, before and after handling food and after contact with any animals and pets, including farm animals. Small children should also be supervised when washing their hands.

The particular strain involved in the outbreak has been identified as phage type (PT) 34.

Published 5 July 2016
Last updated 11 August 2016 + full page history
  1. Updated as outbreak declared over.
  2. Added latest update.
  3. Updated number of confirmed cases and latest advice.
  4. Updated number of confirmed cases and latest advice.
  5. First published.