As far as modern-day villains go, a side salad may not seem all that menacing. Yet researchers now believe that such salads – or more specifically, the contaminated sprouts they contained – were behind the terrifying outbreak of bloody diarrhea and hemolytic-uremic syndrome (HUS) in Northern Germany this past May.
The likely chain of events, as Buchholz et al report in NEJM, came from Shiga toxin-producing Escherichia coli (STEC)-contaminated sprouts from a single producer in lower Saxony in Germany. These sprouts passed to 26 sprout distributors and then on to restaurants, cafeterias, and caterers. In total, more than 40 outbreak clusters, across more than 15 countries, were identified. Over 4,000 illnesses had been documented by late July, including 50 deaths and 800 cases of HUS, a serious disorder characterized by kidney failure, hemolytic anemia, and thrombocytopenia.
To find the culprit, the authors used several investigative methods. First, they conducted a case-control study. Subjects with HUS (n=26) were matched with control subjects (n=81) and asked about their recent history of fruit and vegetable consumption. This identified a significant association between outbreak of illness and the consumption of both cucumbers (which were later exonerated) and sprouts.
The authors then conducted a recipe-based study, focusing on a single restaurant in Germany where many victims of bloody diarrhea had dined during the outbreak period. The authors identified cohorts that had dined at the restaurant and asked all members (n=152) about which menu items they had consumed. They then interviewed the chef to determine which ingredients had gone into various menu items. By analyzing different raw foods, the authors found that only visitors who had been served sprouts seemed more likely to fall ill.
Finally, the authors conducted trace-back and trace-forward investigations, starting with a hotel in lower Saxony that had been identified as an outbreak cluster and that was known to have been served a contaminated “spicy sprout mixture.” The sprouts were traced back to the producer mentioned above. Tracing forward from the producer subsequently identified the 26 distributors. All documented case clusters could be linked to at least one of these distributors.
In an accompanying editorial, Dr. Martin Blaser of the Departments of Medicine and Microbiology at New York University offers this perspective on what can be learned from the epidemic: “In this outbreak, clinicians cared for their patients diligently but without critical knowledge. Would antibiotics help or hurt? Glucocorticoids? Plasma exchange? Just as there is a system for emergency case reporting in Germany and elsewhere, we also need authorizations to conduct clinical trials in real time during public health emergencies such as this one.”
Infectious diseases specialist and NEJM deputy editor Dr. Lindsey Baden states, “Important emerging infectious diseases will continue to occur. We need to learn from these episodes to enable us as a community to respond quickly and accurately to protect the public health and minimize inaccurate information. Our colleagues in Germany and elsewhere have provided valuable information to guide our understanding and to limit this outbreak of STEC/HUS.”
If you were faced with a similar epidemic, what kind of evidence would you find most useful as a clinician? As a community member?