Posted May 22, 2014 3:30 PM ET

May 22, 2014

CDC is collaborating with public health officials in Idaho and Washington and the U.S. Food and Drug Administration (FDA) to investigate a multistate outbreak of Shiga toxin-producing Escherichia coli O121 (STEC O121) infections.

The type of bacteria responsible for this outbreak is among those referred to as Shiga toxin-producing E. coli,or STEC. Some types of STEC frequently cause severe disease, including bloody diarrhea and hemolytic uremic syndrome (HUS), which is a type of kidney failure. STEC bacteria are divided into serogroups (e.g., O157 or O121). E. coli O157 is the STEC serogroup found most commonly in U.S. patients. Other E. coli serogroups in the STEC group, including O121, are sometimes called "non-O157 STECs." Because clinical laboratories typically cannot directly identify non-O157 STEC serogroups, they must first test stool samples for the presence of Shiga toxins. Then, the positive samples must be sent to public health laboratories to look for non-O157 STEC. In recent years, the number of clinical laboratories that test for Shiga toxin has increased greatly, but some laboratories still do not perform these tests. Because of these complexities, many non-O157 STEC infections are probably not identified.

As of May 21, 2014, seven confirmed and three probable cases of STEC O121 infection have been reported in Idaho and Washington. The number of ill persons identified in each state is as follows: Idaho (3) and Washington (7).

Among persons for whom information is available, illness onset dates range from May 1, 2014 to May 13, 2014. Ill persons range in age from 22 years to 45 years, with a median age of 27 years. Ninety percent of ill persons are female. Five (50%) of the 10 ill persons have been hospitalized. No ill persons have developed HUS, and no deaths have been reported.

This outbreak can be visually described with a chart showing the number of persons who became ill each day. This chart is called an epidemic curve or epi curve. Illnesses that began after April 30, 2014 might not yet be reported due to the time it takes between when a person becomes ill and when the illness is reported. This takes an average of 2 to 3 weeks. Please see the Timeline for Reporting Cases of E. coli O157 Infection for more details.

Investigation of the Outbreak

Results from initial state and local epidemiologic investigations indicate a link to eating raw clover sprouts. In interviews, nine (90%) of ten ill persons reported eating raw clover sprouts in the week before becoming ill. This proportion is significantly higher than results from a survey [PDF - 788 KB] of healthy persons in which 8% reported eating raw clover sprouts in the week before they were interviewed.  According to the Washington State Department of Health and the Idaho Department of Health and Welfare, ill persons reported eating sprouts in sandwiches at several local food establishments, including several Jimmy John’s Gourmet Sandwiches locations, the Pita Pit, and Daanen’s Deli.

Preliminary traceback investigations indicate that contaminated raw clover sprouts produced by Evergreen Fresh Sprouts, LLC. of Idaho is the likely source of this outbreak of STEC O121 infections. FDA continues its investigation in order to identify the source of the contamination causing the outbreak.

CDC and state and local public health partners are continuing laboratory surveillance through PulseNet to identify additional ill persons and to interview them about foods eaten before becoming ill. CDC will update the public when additional information is available.

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