How international co-operation curtailed a salmonella outbreak

14 September 2010

Contaminated eggs from a single flock of hens on a Spanish farm were implicated in an upsurge in Salmonella food poisoning notifications in England and Wales over a 16 week period between September and December 2009, delegates to the Health Protection Agency's annual conference - Health Protection 2010 - at the University of Warwick will hear.

Dr. Kulsum Janmohamed, one of the HPA's Public Health Registrars described the detective work, inter-agency and pan-European co-operation that identified and closed down the source of infection.

Presenting her report in the conference's Foodborne Illnesses Symposium, Dr. Janmohamed said: "We were notified about 16 local outbreaks and we tested samples, including egg samples, from these and from sporadic cases. We found that 489 people were infected with Salmonella Enteritidis phage type (PT) 14b. The strains were indistinguishable from egg isolates, suggesting that a single source of infection was likely.

"S. Enteritidis PT 14b with a similar resistance profile has historically been associated with contaminated eggs supplied to the catering sector.

"Epidemiological and microbiological investigations had linked the outbreaks to a number of different catering establishments and to a residential care home. A case-control study confirmed the hypothesis that the infections were linked to food eaten outside the home and to eggs that had been eaten within five days of the onset of symptoms."

Co-operation from egg wholesalers who had supplied restaurants associated with the outbreaks resulted in the identification of eggs that were contaminated with S. Enteritidis PT14b. These eggs had been sourced from a single flock on a Spanish farm.

"We notified the Food Standards Agency (FSA) of all our findings and the FSA in turn notified the European Commission. European authorities alerted the appropriate agencies in Spain and eggs from this source were withdrawn from the market. The European withdrawal of the implicated eggs resulted in our outbreak being contained and we saw a rapid decline in cases in England and Wales," Dr. Janmohamed said.

Justin McCracken, HPA's chief executive, said: "This was a massive investigation at local, national and international level. It's successful outcome was largely a result of successful working partnerships between the HPA's local specialists and their Environmental Health colleagues in local authorities, painstaking work in the laboratories, including the Agency's Salmonella Reference Laboratory, and support from the Food Standards Agency and other partners.

"It was important to alert health professionals and to give advice to the public. The HPA and the National Public Health Service for Wales alerted GPs and other professionals and enlisted their help in identifying new cases. Articles were published in the HPA's Health Protection Report. The FSA posted advice for the public on its website and several national newspapers published reports on the outbreak, all of which helped considerably with our investigation.

"The EEC and the Spanish authorities gave the issue the priority it deserved and their prompt action effectively removed a significant public health risk.

"An important lesson from this episode is that it is vitally important for caterers to heed the well established advice on the safe use of eggs." 

Note to editors

For further information please contact Hugh Lamont, Regional communications Manager, HPA North West on 07764-906508 or the national HPA press office on 0208-327-7098/7750.

About Health Protection 2010

The Health Protection Agency's annual conference - Health Protection 2010 - is being held at the University of Warwick from 14-15 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

Last reviewed: 14 September 2010