• Kai is a contributing correspondent for Science magazine based in Berlin, Germany.

Restaurant Photos Help Nail Sprouts in German Outbreak

10 June 2011 3:50 pm


Exhibit A. This picture and others taken at a German restaurant helped determine the source of the outbreak.

BERLIN—Snapping pictures of your restaurant meal may be an odd habit—but what if it helps save lives? Today, German officials announced that they are now certain that organic sprouts* are the source of the epidemic of enterohemorrhagic Escherichia coli (EHEC) in their country—and diners who took out their cameras before digging in have proven to be a big help.

Early epidemiological studies had shown that EHEC-infected women were a lot more likely to have eaten raw tomatoes, cucumbers, and lettuce prior to their illness than women who remained healthy, and on 25 May the Federal Institute for Risk Assessment (BfR) issued a recommendation to avoid those products. But more recent studies focusing on clusters of infected individuals showed that many patients had eaten at restaurants and cafeterias that had a connection to an organic sprout farm in Bienenbüttel, a village in Lower Saxony. The farm was closed as a precaution and the BfR extended its recommendation to sprouts.

Today, researchers at the Robert Koch Institute (RKI), the German center for disease prevention and control, confirmed the suspicion in what they call a "recipe-based restaurant cohort study." "The problem is that many people do not remember exactly what was in the food they had for lunch or dinner days ago," says Gérard Krause, head of infectious epidemiology at RKI. To address that problem, the researchers identified five travel groups that had eaten at a restaurant in Northern Germany. There were EHEC victims in all five groups; altogether, 19 of the 112 diners had become infected. (The name of the eatery has been kept secret.)

On Tuesday and Wednesday, research teams swarmed out to interview the groups' members. Using order lists, bills, and photos, they managed to determine for most of the guests which items on the menu they had chosen. At the same time, three researchers went to the kitchen to find out how exactly the food was prepared and what ingredients went into each dish. "Only by bridging the memory gaps of the guests with the detailed knowledge of the chefs could we find out exactly what every guest had consumed," says RKI President Reinhard Burger. "Those photos really helped us as well."

The researchers returned to Berlin on Wednesday evening and started entering the data into their computers. A statistical analysis, ready at 6:00 Thursday morning, revealed that people who had eaten sprouts were 8.6 times more likely to have become infected with EHEC than those with sprout-free meals. All 19 guests who had fallen ill had eaten sprouts.

On the strength of this evidence—and because a total of 26 EHEC clusters has been traced back to the sprout farm in Bienenbüttel—the BfR officially exonerated the other vegetables at a press conference here today. Households and restaurants were advised to destroy any sprouts they had in stock and any food that might have come into contact with them.

Hours after the press conference, the minister for agriculture and consumer protection of North Rhine-Westphalia announced that the EHEC bacteria with the specific serotype causing the outbreak, called O104, had for the first time been found on sprouts from the organic farm in Bienenbüttel as well. The sample came from an open package in the garbage of a family in North Rhine-Westphalia, so it cannot be ruled out entirely that the sprouts were contaminated only after they were thrown away—but it's another important piece of evidence. Two people in the household had become infected with EHEC.

Also today, EHEC researcher Helge Karch of the University of Münster confirmed suspicions that the strain of the current outbreak likely originated in humans. EHEC bacteria have a natural reservoir in ruminants such as cows and sheep, which carry the pathogens in their guts and spread them with their feces. But genome analysis of the German strain suggests that it is actually a member of a different, less aggressive class of microbes called enteroaggregative Escherichia coli (EAEC), which turned dangerous when it acquired the so-called Shiga toxin usually found in EHEC bacteria.

"The pathogen that is now spreading has only been found in humans so far," Karch was quoted as saying in a press release. That makes it more likely that this outbreak also originated in a person—who may have carried the microbe without having symptoms—than in a farm animal, Karch believes.

While the number of new infections is now declining, a heated political debate has emerged in Germany on whether the federal institutes involved in disease control and prevention should have more powers. Responsibility for food safety and health currently rests with the country's 16 Bundeslaender, or states; by law RKI and BfR can only offer assistance when asked. Many scientists view that setup as ineffective. In the current outbreak, for instance, communication with the public has at times been chaotic, with simultaneous press conferences announcing different recommendations.

"Viruses and bacteria don't care about [states'] frontiers," says Georg Peters, a microbiologist at the University of Münster. "It would make a lot of sense to create an institution that is in charge in this type of situation" at the federal level. Disease experts have been calling for such an institution for years, but so far, the states have resisted relinquishing their power. "We have had SARS, avian influenza, swine flu, now EHEC," says Peters. "Something has to finally happen."

* This article and its headline have been changed to reflect that bean sprouts were not specifically implicated. Sprouts in general were.

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