Outbreak of Escherichia coli O104:H4 Infections Associated with Sprout Consumption — Europe and North America, May–July 2011

In May 2011, public health authorities in Europe began investigating an outbreak of Shiga toxin-producing Escherichia coli (STEC) O104:H4 infections that ultimately involved more than 4,000 persons in 16 countries. Early in the outbreak, it became evident that international surveillance would be necessary to determine the scope of the outbreak, characterize the disease, and identify the source. This report describes surveillance conducted in the United States, which involved active case-finding, use of laboratory testing protocols specific to non-O157 STEC, interviews to identify potential exposures of interest, and documentation of clinical courses. Six cases in the United States were associated with the outbreak. Although European epidemiologic studies, including analyses of restaurant cohorts and traceback investigations, ultimately implicated raw fenugreek sprouts as the food vehicle, none of the patients in the United States definitively recalled sprout consumption. These events highlight challenges in investigating outbreaks, particularly those caused by rare pathogens or associated with food vehicles that are consumed in small quantities as part of other dishes. Clinical laboratories should adhere to STEC testing recommendations because they are critical for identification of rare or novel STEC pathogens. Robust public health infrastructure is necessary to effectively manage and resolve foodborne outbreaks.