Introduction
CDC collaborated with public health officials in several states and the U.S. Food and Drug Administration (FDA) to investigate a multistate outbreak of Shiga toxin-producing Escherichia coli O157:H7 (STEC O157:H7) infections. Results from this investigation linked this outbreak to pre-packaged leafy greens produced by State Garden of Chelsea, Massachusetts.
Public health investigators used DNA “fingerprints” of E. coli bacteria obtained through diagnostic testing with pulsed-field gel electrophoresis, or PFGE, to identify cases of illness that were part of this outbreak. They used 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 was among those referred to as Shiga toxin-producing E. coli or STEC. STEC bacteria are grouped by serogroups (e.g., O157 or O145). The STEC serogroup found most commonly in U.S. patients is E. coli O157.
A total of 33 ill persons infected with the outbreak strain of STEC O157:H7 were reported from five states. The number of ill people identified in each state with the outbreak strain was as follows: Connecticut (2), Massachusetts (3), New York (26), Pennsylvania (1), and Virginia (1).
Among persons for whom information was available, illness onset dates ranged from October 18, 2012 to November 12, 2012. Ill persons ranged in age from 4 years to 66 years, with a median age of 24 years. Sixty-three percent of ill persons were female. Among 28 ill persons with available information, 13 (46%) were hospitalized. Two ill persons developed hemolytic uremic syndrome (HUS), a type of kidney failure. No deaths were reported.
This particular outbreak appears to be over. However, E. coli is still an important cause of human illness in the United States. More information about E. coli and steps people can take to reduce their risk for infection can be found on the CDC E. coli homepage.
Investigation of the Outbreak
Epidemiologic, laboratory, and traceback investigations conducted by officials in local, state, and federal public health, agriculture, and regulatory agencies linked this outbreak to pre-packaged leafy greens, produced by State Garden of Chelsea, Massachusetts.
State public health officials interviewed ill persons to obtain information regarding foods they might have eaten and other exposures in the week before illness. Thirty (97%) of 31 ill persons reported eating pre-packaged leafy greens. Fifteen (48%) of 31 ill persons for whom information was available reported eating Wegmans brand Organic Spinach and Spring Mix blend in the week before becoming ill. In total, 25 (81%) of 31 ill persons for whom information was available reported eating a variety of different brands of pre-packaged leafy greens produced by State Garden.
Testing conducted by the New York Department Health Wadsworth Center Laboratories isolated the outbreak strain of STECO157:H7 from four leftover packages of Wegmans brand Organic Spinach and Spring Mix blend collected from four ill persons’ homes.
Traceback investigations of pre-packaged leafy greens purchased by ill persons identified State Garden as a common producer, but a source of contamination was not identified. FDA continues its investigation into the source of the contamination.
On November 2, 2012, Wegmans voluntarily recalled its 5-ounce and 11-ounce clam shell packages of Organic Spinach and Spring Mix blend, a product produced by State Garden. State Garden issued a consumer advisory regarding the product packaged on October 12 and 13, 2012.
