HPA investigates a national outbreak of salmonella

17 September 2010

The Health Protection Agency (HPA) has investigated an on-going national outbreak of Salmonella Typhimurium DT8. 

Salmonella Typhimurium DT8 causes a similar illness to other forms of Salmonella infection, so symptoms can include diarrhoea, vomiting, abdominal pain and fever.

So far this year, the HPA has confirmed 66 reports of human infection in England and Northern Ireland.  Figures for previous years were 34 in 2008 and 47 in 2009.   

Of the reported cases two are known to have been hospitalised, one of whom has died. Cases are mainly adults with an average age of 46 years, and most are men (61 per cent).  Cases have been referred from Northern Ireland and most regions in England, with predominance in the South East and North West.   

Dr Dilys Morgan, who is leading the investigation for the Agency, said: “As soon as the Agency first noticed an increase in cases we started detailed investigations using food questionnaires and interviewing cases to find the common cause of illness in these people and to identify the source of the outbreak.

“It became clear from our investigations that the increase was related to the consumption of duck products, mainly eggs. It is important that consumers and caterers are aware that all eggs, including duck eggs, may occasionally be contaminated with Salmonella and follow advice provided by the Food Standards Agency in order to reduce the risk of infection. Eggs should be cooked thoroughly and good hygiene practices, such as washing hands, utensils and kitchen surfaces should be followed after handling or using duck eggs.”

Ends

Notes to editors

Q. What is Salmonella Typhimurium DT8?

A: Salmonella Typhimurium causes a similar illness to other forms of Salmonella infection, and symptoms can include diarrhoea, vomiting, abdominal pain and fever. 

Q: Have there been previous outbreaks of Salmonella Typhimurium?

A.  Recently there has been an outbreak of the same type of Salmonella in Ireland and this was also linked to duck eggs.

Q. How many cases of this kind of Salmonella do you normally see a year?

A. Previous figures for the number of cases of the outbreak strain of Salmonella DT8 that the HPA have recorded in previous years are:
2009: 71
2008: 55
2007: 67
Ave: 64

Q. How severe is this outbreak?

A: Two of the reported cases were hospitalised and one has sadly died. Salmonella can cause very serious illness in the very young and the elderly whose immune system may not be as robust as to be able to fight off the infection. 

Q. What has caused this outbreak?

A. Investigations strongly suggest that cases are related to the consumption of duck eggs and the HPA has working with the Food Standards Agency over the increase in cases and the potential source.

Q: What does the HPA do to investigate outbreaks of salmonella?

A: If there is an outbreak then the first evidence will be an increase in the number of samples submitted to the Reference Laboratory for confirmation and typing

The HPA would then have to establish whether this was an outbreak or whether there could be any other explanations for the increase in cases. 

For example

• Are the cases coming from abroad?
• Have the samples been misclassified in the lab?
• Is there a lab backlog of samples so it appears there is a peak when there is not?

If it still appears there is an outbreak then an Outbreak Control Team is established. Patients are interviewed by epidemiologists using structured questionnaires. These would include descriptive data including personal details of the patients, clinical histories, household details, what food they had eaten and animals they had come into contact with in the seven days before becoming ill and where it was bought, their food preferences and travel histories. 

Based on the evidence from the questionnaires and the telephone interviews if it appears the outbreak is foodborne then an Outbreak Control Team is established.  The HPA then work with other organisations to prevent other people becoming unwell including the Food Standards Agency and Environmental Health.  

Food Standards Agency statement

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Last reviewed: 17 September 2010