Posted April 26, 2013 11:30 AM ET

April 26, 2013

Case Count Update

A total of 32 individuals infected with the outbreak strain of STEC O121 have been reported from 18 states. Five additional ill persons have been reported from California (1), Colorado (1), Florida (2), and Ohio (1).

Among persons for whom information is available, illness onset dates range from December 30, 2012 to April 2, 2013. Ill persons range in age from one year to 75 years, with a median age of 17 years. Eighty-one percent of ill persons are 21 years of age or younger. Fifty-six percent of ill persons are female. Among 26 persons with available information, 9 (35%) reported being hospitalized. Two ill people developed hemolytic uremic syndrome (HUS), a type of kidney failure, and no deaths have been reported.

Illnesses that occurred after March 30, 2013 might not be reported yet due to the time it takes between when a person becomes ill and when the illness is reported.

April 5, 2013

Case Count Update

A total of 27 individuals infected with the outbreak strain of STEC O121 have been reported from 15 states. Three new cases have been reported from Illinois (1), Michigan (1) and New York (1).

Among persons for whom information is available, illness onset dates range from December 30, 2012 to March 18, 2013. Ill persons range in age from 2 years to 75 years, with a median age of 17 years. Eighty-one percent of ill persons are 21 years of age or younger. Fifty-six percent of ill persons are female. Among 23 persons with available information, 8 (35%) reported being hospitalized. Two ill people developed hemolytic uremic syndrome (HUS), a type of kidney failure, and no deaths have been reported.

Illnesses that occurred after March 10, 2013 might not be reported yet due to the time it takes between when a person becomes ill and when the illness is reported.

Investigation Update

Twenty (100%) of 20 ill persons interviewed reported consuming frozen food products. Ten (63%) of 16 ill persons reported consuming Farm Rich brand frozen food products. Investigations are ongoing to determine the specific types and sources of frozen food that might be linked with illness, as well as to determine which particular ingredients or components of these products may be contaminated.

Testing conducted by the Outbreaks Section of the USDA-FSIS Eastern Laboratory identified the outbreak strain of STEC O121 from individually wrapped Farm Rich brand frozen mini pizza slices from an opened package collected from an ill person’s home in Texas. The frozen mini pizza slices were included in the products that were recalled on March 28, 2013.

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March 29, 2013

CDC is collaborating with public health officials in many states, the U.S. Department of Agriculture’s Food Safety and Inspection Service (USDA-FSIS), and the U.S. Food and Drug Administration (FDA) to investigate a multistate outbreak of Shiga toxin-producing Escherichia coli O121 (STEC O121) infections. Public health investigators are using DNA "fingerprints" of E. coli bacteria obtained through diagnostic testing with pulsed-field gel electrophoresis, or PFGE, to identify cases of illness that could be part of this outbreak. They are using data from PulseNet, the national subtyping network made up of state and local public health laboratories and federal food regulatory laboratories that performs molecular surveillance of foodborne 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. The STEC O121 PFGE pattern in this outbreak is rare. In the past it has been seen less than 30 times in PulseNet.

A total of 24 individuals infected with the outbreak strain of STEC O121 have been reported from 15 states. The number of ill persons identified in each state is as follows: Alabama (1), Arkansas (1), Illinois (1), Indiana (2), Michigan (2), Mississippi (1), New York (3), Ohio (3), Pennsylvania (1), South Dakota (1), Texas (3), Utah (1), Virginia (1), Washington (1), and Wisconsin (2).

Among persons for whom information is available, illness onset dates range from December 30, 2012 to March 9, 2013. Ill persons range in age from 2 years to 75 years, with a median age of 17 years. Seventy-eight percent of ill persons are 21 years of age or younger. Sixty-three percent of ill persons are female. Among 21 persons with available information, 7 (33%) reported being hospitalized. One ill person developed HUS, and no deaths have been reported.

The outbreak can be visually described with a chart showing the number of people who became ill each day or week. This chart is called an epi curve. Illnesses that occurred after March 1, 2013 might not be reported yet 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. For more details, please see Timeline for Reporting E. coli Cases.

Investigation of the Outbreak

Epidemiologic, laboratory, and traceback investigations conducted by officials in local, state, and federal public health, agriculture, and regulatory agencies indicate that Farm Rich brand frozen food products are one likely source of this outbreak of STEC O121 infections.

In interviews, ill persons answered questions about food consumed and other exposures during the week before becoming ill. Eighteen (100%) of 18 ill persons interviewed reported consuming frozen food products. Eight (57%) of 14 ill persons reported consuming Farm Rich brand frozen food products. Investigations are ongoing to determine the specific types and sources of frozen food that might be linked with illness, as well as to determine which particular ingredients or components of these products may be contaminated.

The New York State Department of Health, Wadsworth Center Laboratory, identified the outbreak strain of E. coli O121 in an opened package of Farm Rich brand frozen mini chicken and cheese quesadillas from an ill person’s home.

CDC and state and local public health partners are continuing laboratory surveillance through PulseNet to identify additional ill persons and to interview ill persons about foods eaten before becoming ill. FSIS and FDA are continuing to work closely with CDC and state partners during this investigation.

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