In the latest installment of, we told ya so (but we’d never say that), the U.S. Centers for Disease Control reports that 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.

During May 26–June 16, six confirmed cases were identified in five states: Arizona (one), Massachusetts (one), Michigan (two), North Carolina (one), and Wisconsin (one). Ages of patients ranged from 38 to 72 years (median: 52 years); two patients were female. Five reported travel to or from Germany in the 3 weeks before their illness; the additional secondary case was in a close relative of a patient who had traveled. Patients reported consumption of various fresh produce items while in Germany, such as tomatoes, lettuce, and cucumbers. However, none recalled consumption of sprouts, the food vehicle ultimately implicated in the outbreak. All patients had diarrhea, including four (66%) with bloody diarrhea. Four (66%) patients were reported by physicians to have developed HUS, requiring dialysis and ventilator support. One patient died.

Microbiologic characterization of the pathogens isolated from clinical specimens demonstrated STEC O104:H4 within all specimens, with a PFGE pattern indistinguishable from the outbreak strain. This strain combines features of the STEC and enteroaggregative (EAEC) pathotypes of Escherichia coli. All isolates were positive for the stx2a gene, which encodes a Shiga toxin variant often associated with severe E. coli illness, such as bloody diarrhea or HUS (7). Additionally, all isolates were positive for the aggR gene, which encodes a regulator of virulence plasmid and chromosomal genes and is characteristic of EAEC (7). The strains were negative for the eae gene, which encodes a mucosal adherence protein in most STEC (7). Isolates from the six patients had almost identical antimicrobial resistance profiles; all were resistant to ampicillin, ceftriaxone, streptomycin, sulfisoxazole, tetracycline, and trimethoprim/sulfamethoxazole.

On July 5, 2011, the European Union banned importation of fenugreek seeds and various other seeds, beans, and sprouts from Egypt. Worldwide surveillance continued for an additional 3 weeks, but no new cases were identified. On July 26, public health authorities in Germany declared the outbreak to be over. The final case count was 4,075 cases (including 908 cases complicated by HUS) and 50 deaths in 16 countries.