Conference hears how bean sprouts were identified as the vehicle of transmission in national S. Bareilly outbreak

14 September 2011

Delegates to the Health Protection Agency's annual conference (Health Protection 2011) at the University of Warwick today (Wednesday 14 September) heard about the detective work that identified raw bean sprouts as the main vehicle of transmission in a national outbreak of Salmonella Bareilly food-poisoning.

Delegates were told that 241 cases of S. Bareilly had been reported in England, Scotland, Wales and Northern Ireland between August and December 2010. One of the patients died.

Dr. Paul Cleary, Regional Epidemiologist with HPA North West who led the epidemiological investigations on behalf of a multi-agency outbreak control team, said: "It became apparent early in the investigation, largely as a result of a national case control study, that bean sprouts were significantly associated with the transmission of infection. These early findings were confirmed when Salmonella Bareilly isolated from bean sprout samples in England and Scotland was found to be indistinguishable from isolates from the human cases."

Dr. Cleary's presentation to Health Protection 2011 coincides with publication of the outbreak control team's report on the outbreak, which describes how the authorities first became aware of the situation when there was an outbreak of food-borne illness following a wedding reception in North Manchester. It soon became apparent that there was also an outbreak in Scotland and sporadic cases throughout England and in Wales and Northern Ireland.

Laboratory tests confirmed that the outbreak strains of S. Bareilly in Manchester and Scotland were indistinguishable from each other, and also indistinguishable from the sporadic cases elsewhere in England and Wales.

Investigations by Environmental Health Officers (EHOs) and the HPA's Food, Water and the Environment (FW & E) Laboratory in Preston led to the conclusion that the implicated bean sprouts had been grown from contaminated seeds that had been imported to the UK.

"Once we established that bean sprouts were the probable vehicle of transmission, our main interventions were to give advice to the public and, through environmental health professionals, to bean sprout growers, wholesalers, retailers and catering establishments," Dr. Cleary said.

 "A key focus was to ensure that the labeling on packs of bean sprout and salad vegetables containing bean sprouts was clear and unambiguous. Our colleagues at the Food Standards Agency worked with the seeded sprout growers, wholesalers and retailers through the local authority EHO network to ensure that labeling that could have been misleading, such as "washed and ready for use", was changed to "washed and ready to cook", to cite one example."

Dr. Joe Kearney, an HPA regional director who chaired the multi-agency outbreak control team, said: "The fact that we discovered a probable association with bean sprouts so early in the investigation enabled our colleagues at the FSA to issue timely advice to the catering industry. This advice was repeated and strengthened as the evidence linking contaminated bean sprouts to the outbreak became stronger. At the same time, we gave important information to the public through the news media.

"Our key message was and continues to be that bean sprouts are safe to eat provided that they are washed and cooked through until they are piping hot, unless they are clearly labeled as ready-to-eat. Raw and undercooked bean sprouts can potentially pose a risk to health."

Notes to editors

To view the presentation abstract, visit: http://www.hpa-events.org.uk/hpa/frontend/reg/absViewDocumentFE.csp?popup=1&documentID=4458&eventID=127

The outbreak control team was composed of representatives from the HPA's Health Protection and Microbiology Services, Health Protection Scotland, the Food Standards Agency and EHOs from a number of local authorities.

This outbreak was not related to the outbreaks in Germany or France earlier this year which were caused by a different strain of E. coli called O104.

The report of the outbreak can be accessed on the HPA's website from the Publications pages, under Infection Control: http://www.hpa.org.uk/Publications/InfectiousDiseases/InfectionControl/

Information on Salmonella is available on the Health Protection Agency's website: http://www.hpa.org.uk/Topics/InfectiousDiseases/InfectionsAZ/Salmonella/

The FSA advice on the safe preparation of bean sprouts may be accessed via: http://www.food.gov.uk/ 

A summary of the FSA advice with regards to bean sprouts is:

• Bean sprouts should be cooked until piping hot unless they are labeled as ready-to-eat.
• As a precautionary measure it is advised that even bean sprouts labeled as ready-to-eat should be thoroughly cooked if they are to be served to young children, elderly people, people with impaired immune systems and pregnant women. 
• People who prepare meals in catering establishments and in the home should keep raw bean sprouts separate and apart from other salad produce, including bean sprouts that are labeled as ready-to-eat, to avoid the risk of cross-contamination.
• If this advice is followed bean sprouts will be safe to eat.

It is critically important for people to wash their hands before eating or preparing food; after handling raw meat or poultry; after using the toilet; after changing nappies or cleaning up after others with diarrhoea. Hand-washing after contact with animals is essential. Children who have touched animals should be supervised when washing their hands.

About Health Protection 2011

The Health Protection Agency's annual conference - Health Protection 2011 - is being held at the University of Warwick from 13-14 September. The conference offers a variety of innovative presentations which will demonstrate the latest scientific research and its practical application in three key areas of health protection - preventing and reducing infectious diseases, minimising the impact of radiation, chemical and environmental hazards and preparing for potential or emerging threats to health. To find out more information visit: www.healthprotectionconference.co.uk

About the Health Protection Agency

The Health Protection Agency is an independent UK organisation that was set up by the government in 2003 to protect the public from threats to their health from infectious diseases and environmental hazards. In April 2013, subject to the usual approvals procedures for establishing new bodies, the Health Protection Agency will become part of a new organisation called Public Health England, an executive agency of the Department of Health. To find out more, visit our website: www.hpa.org.uk

Press release issued by the communications team, HPA North West. For further information please call 0844-2251295 and select option 2 or contact the HPA's national press office on 0208 327 7901. Out of hours the national duty press officer can be reached on 0208 200 4400.

Last reviewed: 13 September 2011