Raw loose leeks and sacks of potatoes spread a dirty little secret this year in England, Scotland and Wales – an unusual subtype of E. coli O157 known as Phage Type 8 (PT8).

In an outbreak of illnesses that began in December 2010 and continued into July, the Health Protection Agency, Health Protection Scotland and Public Health Wales received a total of 250 reports of illnesses caused by this strain of E. coli O157. Most cases were described as “mild to moderate”; nevertheless, 74 people visited hospital for assessment or treatment, four people developed Hemolytic Uremic Syndrome, and one patient with underlying health problems died.

The majority of the illnesses were reported in England (193 cases); Scotland reported 44 cases, and Wales had 14. No cases were reported in Northern Ireland. Forty percent (40%) of the patients were under 16 years old.

Determining the common link in this outbreak was a difficult job for the multi-agency Outbreak Control Team that was charged with the investigation. It took a six-month long investigation and an in-depth statistical case control study to uncover the likely source of the contamination. The Team interviewed 30 patients and 62 controls (healthy individuals), and found two statistically significant differences between the two groups:

1. Ill people were 40 times more likely than the control group to have been in a household where people handled leeks that were not prepackaged (i.e., sold loose)
2. Ill people were 12 times more likely to have been in a household where people handled potatoes bought in, or sold from, sacks.

Anyone who has ever peeled potatoes or prepared leeks knows that they often have soil and grit clinging to them. The Outbreak Control Team suspects that contaminated soil from leeks or potatoes may have cross-contaminated during storage in the home.

The leek and potato E. coli O157 outbreak – like this year’s multi-national E. coli O104:H4 outbreak that was traced to contaminated fenugreek seeds, and the UK sprout-related Salmonella outbreak –  is a very direct and graphic illustration of the importance of environmental contamination of vegetables and fruit in the spread of food-borne diseases. Yet, in spite of the publicity given to these outbreaks, many consumers still do not associate raw vegetables with food safety risks.

A “Consumer Engagement” research report on E. coli and vegetables, released by the UK Food Standards Agency in mid-September, contained several conclusions, including:

• Although, on reflection, consumers recognised specific food safety risks, concerns about food poisoning and bacteria was not top-of-mind when handling vegetables.
• Raising awareness of the risk of bacteria in soil would reinforce existing practices without causing undue concern or creating new anxieties relating to food.
• Consumers need more information about the risks of handling vegetables, in particular highlighting that bacteria on the skin can cause cross-contamination in people‟s homes. This coupled with a clear explanation of how food hygiene practices combat these risks will help to address existing knowledge gaps.
• Consumers need more information about the risks of handling vegetables, in particular highlighting that bacteria on the skin can cause cross-contamination in people‟s homes. This coupled with a clear explanation of how food hygiene practices combat these risks will help to address existing knowledge gaps.

The Food Standards Agency offers a number of tips for preparing and handling food safely in the home, including these suggestions for reducing the risk of cross-contamination:

• Remove any loose soil before storing vegetables and salads to avoid cross contamination of clean items.
• Thoroughly wash all vegetables (including salads) that will be eaten raw unless they have been pre-prepared and are specifically labelled ‘ready to eat’.
• Do not prepare raw vegetables with utensils that have also been used for raw meat.
• Keep raw meat and unwashed vegetables away from ready-to-eat foods during storage and preparation.
• Use different chopping boards, knives and utensils for raw and ready-to-eat foods, or ensure they are washed thoroughly between uses.
• Wash your hands thoroughly after handling raw food – including meat and unwashed vegetables. Always wash your hands thoroughly before preparing food, particularly after using the toilet (or helping others including changing nappies), before meals, and after contact with animals or their environments.