Why cucumbers first got the blame

In May this year an outbreak of gastroenteritis was identified by German officials. As soon as it was identified the hunt was on to find the source of the outbreak and to limit the risk of illness in the population. The first suspect was identified was cucumbers from Spain.

Immediately consumers were told to dispose of cucumbers and, just to be safe, tomatoes and lettuces, from Spain. Consumption of salad vegetables took an immediate dive and fresh produce ended up in landfill all over Europe.

Ultimately, the cause of the outbreak was found to be fenugreek sprouts - not cucumbers at all. So how did the Germans get it so wrong? How did they come to blame the innocent cucumber and, as a consequence, devastate the entire salad produce market in Europe?

This outbreak of foodborne illness was not mild and not typical. By the end of July 2011, a total of 3816 cases including 54 deaths and 845 incidents of haemolytic-uremic syndrome (HUS) had been reported. The incidence of HUS at 22% was unusually high. Also, those affected did not follow the typical trends where children and the immune-compromised are most likely to be affected. In this outbreak adults, especially women, were being affected.

As cases of gastroenteritis were reported, following standard protocol, sufferers were questioned about what they had consumed. Among case subjects, 88% reported having eaten cucumbers while only 25% reported having eaten sprouts. Cucumbers were assumed to be the source of the disease and public warnings issued.

Following an extensive matched case-control study and a recipe-based restaurant cohort study, along with environmental, trace-back, and trace-forward investigations, sprout consumption explained 100% of cases. The problem was that consumers didn’t recall eating sprouts as readily as they recalled eating cucumbers.

In future foodborne illness outbreaks, consideration will have to be given to food items that consumers are less likely to remember.

Two very interesting articles about the German Outbreak of Escherichia coli O104:H4 can be found in The New England Journal of Medicine, 10 November 2011, Vol. 365 No. 19. Both are well worth the read.