None of the US patients recalled consumption of raw fenugreek sprouts, the vehicle of the 2011 outbreak, said the agency’s Morbidity and Mortality Weekly Report (MMWR).
The report summarizes the second-largest shiga toxin–producing E.coli (STEC) outbreak worldwide and the first documented STEC O104:H4 illnesses in the US.
The outbreak, which killed 50 and sickened 4,000, was centred in Northern Germany but affected 16 countries in Europe and North America.
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, two patients were female and five reported travel to or from Germany in the three weeks before their illness.
Patients reported consumption of fresh produce while in Germany, such as tomatoes, lettuce, and cucumbers. However, none recalled eating sprouts, the food vehicle ultimately implicated.
“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,” said the report.
“Clinical laboratories should adhere to STEC testing recommendations because they are critical for identification of rare or novel STEC pathogens.”
Four (66%) patients were reported by physicians to have developed HUS, requiring dialysis and ventilator support and one patient died.
Surveillance involved case-finding, use of laboratory testing protocols specific to non-O157 STEC, interviews to identify potential exposures of interest, and documentation of clinical courses.
Researchers from Michigan State University later decoded the E.coli strain, finding increased production of Shiga toxin was the probable reason for its virulence as it has a longer incubation period.
The European Union banned importation of fenugreek seeds and other seeds, beans, and sprouts from Egypt on 5 July 2011.
Illness onsets began in early May and cases were concentrated in northern Germany.
Case counts mounted rapidly and by 1 June 1,534 were identified, including 470 (31%) complicated by hemolytic uremic syndrome (HUS).
The final case count was 4,075 cases (including 908 complicated by HUS) and 50 deaths in 16 countries.