Today, Kai Kupferschmidt of Science Insider reported that the Robert Koch Institute (RKI) has confirmed that there are now nearly 140 patients in Germany who have developed Hemolytic Uremic Syndrome (HUS) since the second week of May as a result of enterohemorrhagic E. coli (EHEC) infection, compared with the estimated 60 HUS cases that occur in an average year. Klaus Stark, head of the gastrointestinal infections zoonotic diseases division at RKI said, “This is one of the biggest EHEC outbreaks in the world, certainly the biggest one we have ever had in Germany.”

Currently, German officials have identified the serotype of EHEC in stool samples from five patients as O104. Although German scientists continue to search for the source of the outbreak; the rare O104 serotype could prove to be a hindrance to the investigation. Lothar Beutin, head of the National Reference Laboratory for E. coli at the Federal Institute for Risk Assessment in Berlin, Germany, explained that “O104 is very hard to distinguish from normal, non-pathogenic E. coli.”

Despite the challenges they are facing in pinpointing a source, scientists report that they may have a lead. Stark noted, “When [RKI] first interviewed patients, a lot of them mentioned eating raw vegetables.” However, he explained “that does not mean that vegetables are the source.” RKI is hoping that using a detailed questionnaire will aid the investigation. In addition, German epidemiologists were dispatched to Hamburg where they went door to door where some patients live, looking for roughly matching controls. Stark stated, “If we get a clear signal, something that 90% of the cases but only 10% of the controls ate, then we can be very sure that we have found the source.”

Consumer Affairs Minister Ilse Aigner and Health Minister Daniel told the media at a press conference on Wednesday, May 25, 2011, that the situation in Germany remains “threatening.” However, they both expressed confidence that RKI would identify what caused the outbreak. “We are optimistic that we will soon be bordering on being able to say where the source is,” said Aigner.