German health authorities are pointing once again to raw sprouts as the likeliest source of an ongoing outbreak of Enterohemorrhagic E. coli, or EHEC, which has to date caused 31 confirmed deaths and more than 3,000 cases in the European Union, the vast majority of them in Germany.
Epidemiologists at the German government’s Robert Koch Institute in Berlin acknowledged that samples from a sprout farm suspected earlier this week to be the source had turned up negative for the EHEC strain. But the outbreak pattern corresponds to the sprouts being the culprit, investigators said.
In a German-language statement issued June 10, the institute urged restaurants and households not to buy bean or seed sprouts, which they said their epidemiological investigations had determined nonetheless to be the likeliest source of the outbreak, now in its sixth week of cases. The Institute also lifted its earlier recommendations concerning lettuce, tomatoes and cucumbers, saying they need no longer be avoided.
Over the past several weeks, the Koch Institute has conducted a number of analyses and case-control studies trying to identify the infection source, with nearly all of the suspicion on vegetables.
On June 10, RKI reported results from an analysis of a 112-person cohort of five groups that had eaten at a single restaurant, which revealed an 8.6-fold higher risk of EHEC illness for subjects who had consumed sprouts. Investigators had conducted extensive interviews with diners and kitchen workers, and even consulted photographs from groups taken while dining at the restaurant. A day earlier, the institute released results from a case study in which less than a third of sickened patients reported having eaten sprouts.
The institute also said that its mathematical modeling had revealed that despite a number of new EHEC and hemolytic uremic syndrome (HUS) cases, a declining trend was now observable, but that it did now know whether this was due to avoidance of raw vegetables or the drying up of the infection source.
Also June 10, the European Center for Disease Prevention and Control, in collaboration with the European Food Safety Authority, issued a technical report on E. coli in the European Union with a special focus on shigatoxin-producing EC O104, the strain responsible for the current outbreak.
Data on STEC O104 "is very scarce as this is a very rare serogroup in humans in Europe and the entire world," the report noted, with only 27 cases reported between 1987 and the onset of the current outbreak. For all but one of these cases, which pointed to milk, the precise source of infection was unknown, and four of the cases were preceded by foreign travel to Central Asia, Turkey, and North Africa.
In recent days the German health authorities have come under criticism for what has been considered a belated and disjointed response to the outbreak, which began in early May but was not reported to the ECDC for more than two weeks afterward. State health authorities in Germany have faced particular scrutiny for announcing likely infection sources, including cucumbers imported from Spain, without bacteriological evidence, resulting in Germany’s response being condemned in the European Parliament.
More recently the ECDC itself has come under criticism for its own low profile during the outbreak. "Coordination of the German public health response seems to have been utterly absent," wrote editors for the Lancet in a June 10 editorial (doi:10.1016/S0140-6736(11)60846-5). "But one should also ask: where was the [ECDC]?"
Set up in 2005, the ECDC’s role is to work "in close collaboration with the Member States and the [European] Commission to promote the necessary coherence in the risk communication process on health threats," the Lancet editors wrote. "From the public's point of view, no visible collaboration seems to have taken place."
ECDC has provided the case definition used in the outbreak and has published daily updates on laboratory confirmed cases and deaths for the E.U. as a whole.
In an e-mail interview, a spokeswoman for ECDC described the agency’s response to the outbreak as having "closely monitored the outbreak since it was first reported by the German authorities" May 22, and "supporting the activities being led by the Germany authorities given the EU dimension of this outbreak. Specifically, an ECDC expert was seconded to [the Koch Institute] on 1 June to act as a liaison and to support activities, such as ongoing epidemiological surveillance and verifying the results, and contributing to the ongoing investigations to speed up the identification of the source of the outbreak."
The ECDC has also sent its chief scientist heading of its food and waterborne disease program to Germany June 5 "to get an overview of the situation and support existing German activities," the spokeswoman said.