On Friday, October 18, 2013, public health investigators at the Colorado Department of Public Health (CDPHE) detected an increase in Denver area patients reported as having E. coli O157. Preliminary interviews revealed that patients had eaten at Jimmy John’s restaurants and shopped at an area grocery store chain. CDPHE epidemiologist, Nicole Comstock, noted in an October 22 email sent to county health departments that “at this time we are not ruling any exposures out yet.” Ms. Comstock encouraged county investigators to interview newly reported patients diagnosed with E. coli O157 promptly using a standardized questionnaire. By October 23, CDPHE epidemiologists described the association between illness and sandwiches prepared at area Jimmy John’s restaurants “too strong to ignore.”
CDPHE and their local and federal public health partners conducted case finding, two case control studies (“Study I” and “Study II”), an environmental investigation, produce traceback, and laboratory testing. Case finding occurred via routine public health surveillance methods. Case control “Study I” was conducted to assess restaurant exposures reported by case-patients. Case control “Study II” was conducted subsequently to assess foods consumed at Jimmy John’s. For “Study II” online and phone order records were used to recruit controls (non-ill Jimmy John’s customers) who purchased food from the same Jimmy John’s locations on the dates as case-patients.
Eight patients laboratory confirmed with E. coli O157:H7 were identified as outbreak associated cases. All eight patients were infected with an indistinguishable genetic strain (EXHX01.0074/EXHA26.0569) of E. coli O157 as determined by PFGE and MLVA. This strain was not seen elsewhere in the United States in October 2014. One patient was classified as a “probable” case since she was not culture positive for E. coli O157 due to collection of her stool specimen post-antibiotic treatment. Three blood specimens collected from her would later test positive for IgG and IgM antibodies to E. coli O157:H7, confirming a recent acute infection with E. coli O157. All nine outbreak-associated-cases ate food from one of three Jimmy John’s locations in the metro-Denver area. This finding was highly statistically significant based on analysis of data collected in Case control Study I. Case control Study II data showed that all nine outbreak-associated-cases consumed cucumbers on Jimmy John’s sandwiches, also a highly statistically significant finding. No other food items were statistically associated with illness. Meal dates for case patients were October 5th, 6th, 7th and 9th. Median age of patients was 23 years; 78% were female.
Three (3) Jimmy John’s locations were identified by patients. One was located in Lakewood, Colorado at 180 South Union and was inspected by the Jefferson County Health Department (JCHD). Two (2) fell within the jurisdiction of the Tri-County Health Department (TCHD): 2610 West Belleview Avenue, Littleton, Colorado and 1140 South Colorado Boulevard, Glendale, Colorado. Local health environmental health staff conducted on-site investigations at each restaurant. They examined produce-handling practices and obtained invoices for traceback. Colo-Pac Produce Inc. (“Colo-Pac”) delivered whole cucumbers and other produce to all three stores approximately two times a week. Cucumbers and other produce (lettuce, tomatoes and onions) were washed, chopped, and prepared fresh daily for use at each restaurant. Although no restaurant had leftover food from the implicated meal dates, TCPH and JCHD staff collected food samples for laboratory testing at the CDPHE Public Health Laboratory. All food tests were negative for the presence of E. coli O157 at the state laboratory.
Based on customer purchase order number/bills of lading provided by Colo-Pac, investigators determined that a single lot (Lot 19158) of cucumbers was delivered to all three implicated Jimmy John’s locations during the time frame of interest (September 9, 2013 to October 9, 2013). Further traceback showed that the cucumbers were grown in Torreon, Coahulia, Mexico by grower/packer Ganadera Vigo. They were imported into the United States by GR Produce of McAllen, Texas, which then sold full cases to Colo-Pac. Colo-Pac sold full cases to two of the implicated Jimmy John’s; one store received split cases boxed at Colo-Pac. CDPHE staff conducted an onset inspection at Colo-Pac and obtained 55 swab samples from the warehouse and delivery trucks. All specimens were negative for E. coli O157.