Searching for Causes of 2011 E. coli Outbreak in Europe: Natural, Accidental, or Intentional?

The Escherichia coli outbreak in Europe in 2011, officially assumed to be from a natural origin, may instead have been caused by accidental or intentional introduction of the pathogen into the food chain, a recently published analysis suggests.

The source of the outbreak that sickened more than 4,000 people, including 855 with hemolytic uremic syndrome (HUS), was identified as a single shipment of 15,000 kg of contaminated fenugreek seeds from Egypt. The sprouts from the seeds were assumed to be the vehicle for the deadly outbreak of Shiga toxin-producing E. coli 0104:H4 infections. More than 50 deaths were attributed to the outbreak.

Now researchers in Serbia and Germany have analyzed the possible origins of the outbreak using three models designed to differentiate between unnatural and natural infectious disease outbreaks. Their analysis was published online ahead of print by the European Journal of Public Health. One model, which focuses on outbreak characteristics, determined that the outbreak had features of accidental or intentional epidemics: It affected a high percentage of previously healthy adults who had a severe course of the disease, there were no coexisting syndromes in most patients affected, and a new pathotype of E. coli 0104:H4 emerged.

A second model considered political, demographic, epidemiologic, hygienic, and other data. With that model, the investigators determined that the likelihood of a deliberate release of the pathogen was doubtful. A third model used epidemiologic, infectious, and forensic clues to determine the likely origin of the outbreak. Analysis using that model determined that the outbreak was probably a natural one but that it mimicked accidental or deliberate epidemic events in some epidemiologic and microbiologic features.

The researchers say their analysis with the three models indicates that “the generally accepted assumption that [the outbreak] in 2011 was a natural one may not be accepted without reserve. This is the first time ever that an E. coli 0104:H4 pathotype of a high virulence suddenly emerged, which may indicate an unnatural phenomenon.”

Researcher Vladan Radosavljevic, PhD, of the Military Academy, University of Defense in Belgrade, Serbia, says that the outbreak was worsened due to the long period of time expended to locate the farm production facilities responsible for the contamination, as well as an “inability to prevent so many secondary transmission cases.”

Future research to find the precise causes of the outbreak should include a feasibility study, Dr. Radosavljevic tells Food Quality & Safety.

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