According to the CDC and FDA, the true number of sick people in the walnut E. coli O157:H7 outbreak is likely much higher than the number reported, and the outbreak may not be limited to the states with known illnesses. According to a FoodNet study, for E. coli O157:H7, a pathogen that typically causes bloody diarrhea, the degree of underreporting has been estimated at ~20 fold.[1]

The CDC and FDA have reported that as of April 30, 2024, 12 people infected with E. coli O157:H7 have been reported from Washington and California. Two patients have developed hemolytic uremic syndrome (HUS), a serious condition that can cause kidney failure. The FDA determined that Gibson Farms, Inc., of Hollister, California was the supplier of organic walnuts that were distributed to multiple natural food and co-op stores across the United States and sold in bulk bins.Illnesses started on dates ranging from February 1, 2024, to April 4, 2024. Of 11 people with information available, 7 (64%) have been hospitalized. Walnuts were distributed to these 19 states: Alaska, Arkansas, Arizona, California, Colorado, Hawaii, Idaho, Kansas, Louisiana, Montana, Nebraska, New Mexico, Nevada, Oregon, South Dakota, Texas, Utah, Washington and Wyoming. Click here to find the full list of stores that may have sold the walnuts. Investigators used DNA fingerprinting that revealed bacteria from sick people’s samples as closely related genetically. This suggests that people in this outbreak got sick from the same food, namely Gibson Farms, Inc., walnuts.

According to a recent study, an estimated 93,094 illnesses are due to domestically acquired E. coli O157:H7 each year in the United States.[2] Estimates of foodborne acquired O157:H7 cases result in 2,138 hospitalizations and 20 deaths annually.[3] The colitis caused by E. coli O157:H7 is characterized by severe abdominal cramps, diarrhea that typically turns bloody within twenty-four (24) hours, and sometimes fevers.[4] The incubation period—which is to say the time from exposure to the onset of symptoms—in outbreaks is usually reported as three (3) to four (4) days, but may be as short as one (1) day or as long as ten (10) days.[5] Infection can occur in people of all ages but is most common in children.[6] The duration of an uncomplicated illness can range from one (1) to twelve (12) days.[7] In reported outbreaks, the rate of death is 0-2%, with rates running as high as 16-35% in outbreaks involving the elderly, like those have occurred at nursing homes.[8]

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[1]           Hedberg C, Angulo F, Townes J, Vugia D, Farley M, FoodNet. Differences in Escherichia coli O157:H7 annual incidence among FoodNet active surveillance sites. Baltimore, MD; 1997 June 22-26, 1997.

[2]           Scallan E, et al. Foodborne illness acquired in the United States –major pathogens, Emerging Infect. Dis. Jan. (2011),

[3]           Id., Table 3.

[4]           Griffin & Tauxe, supra note 12, at 63.

[5]           Centers for Disease Control, Division of Foodborne, Bacterial and Mycotic Diseases, Escherichia coli general information, also PROCEDURES TO INVESTIGATE FOODBORNE ILLNESS, 107 (IAFP 5th Ed. 1999) (identifying incubation period for E. coli O157:H7 as “1 to 10 days, typically 2 to 5”).

[6]           Su & Brandt, supra note 11 (“the young are most often affected”).

[7]           Tauxe, supra note 25, at 1152.

[8]           Id.