The CDC reported on December 11, 2013, a total of 33 persons infected with the outbreak strain of E. coli O157:H7 were reported from four states.  The number of ill persons identified in each state was as follows: Arizona (1), California (28), Texas (1), and Washington (3).  32% of ill persons were hospitalized. Two ill persons developed hemolytic uremic syndrome (HUS), and no deaths were reported.

Epidemiologic and traceback investigations conducted by local, state, and federal officials indicated that consumption of two ready-to-eat salads, Field Fresh Chopped Salad with Grilled Chicken and Mexicali Salad with Chili Lime Chicken, produced by Glass Onion Catering and sold at Trader Joe’s grocery store locations, was the likely source of this outbreak of E. coli O157:H7 infections.

On June 17, 2014, the California Department of Public Health Report that concluded that:

An outbreak of E. coli O157:H7 infections occurred in October and November of 2013, affecting 33 individuals in four western states.  The outbreak disproportionately affected California residents, accounting for 85 percent of all case-patients. Two varieties of prepackaged RTE salads produced by “Company A” (Atherstone Foods – Glass Onion Catering) and sold by “GCA” (Trader Joe’s) were implicated as the source of infection.  This is supported by the statistically significant association of case-patients with consumption of one of the two implicated “GCA” salad varieties and by the regional distribution of reported cases matching the regional distribution of these two salads.  No other food items or exposures were associated with illness.  While these salads were strongly associated with the outbreak, the exact source of the contamination remains undetermined.

Today the Food and Drug Branch – Emergency Response Unit – of the California Department of Public Health produced the Environmental Investigation of an E. coli O157:H7 Outbreak in October 2013 Associated with Pre-packaged Salads. The report 28 pages long with several hundred pages of attachments, traces the consumption of the salads to the possible source of the E. coli O157:H7 contamination.

This report not only implicates the two varieties of prepackaged salads noted above, but also two others – one produced by Atherstone Foods – Glass Onion Catering – and another produced by an unnamed manufacturer in Oakland – both for sale at Walgreens.

The investigators concluded that the one common item between the two manufacturers and the four salads was romaine lettuce from a single filed in Modesto, California grown by Ratto Bros.  Five of 44 environmental samples collected in areas around the implicated farm tested positive for E. coli O157:H7, however, the “positive samples were not a genetic match to the outbreak strain” – not a match to the ill people.