The first report of symptoms was by two employees of Jimmy John’s of Boulder who had previously consumed food at their location. Despite being symptomatic with diarrhea, both employees continued to work in a capacity where they handled food. By September 23, 2008, others who had consumed food from that Jimmy John’s location were beginning to experience symptoms.
Upon learning that a significant number of E. coli O157:NM cases had reported eating at Jimmy John’s prior to the onset of symptoms, BCPH investigated Jimmy John’s locations in Boulder and Westminster, and obtained delivery information pertaining to sprouts, lettuce, and tomatoes. On September 26, 2008, BCPH issued a Health Advisory statement reporting their ongoing investigation of the outbreak. Using a cohort study, BCPH determined that the most likely initial source of the E.coli was from sprouts.