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Red Book Online Outbreaks: E. coli Outbreak Linked to Organic Walnuts

July 11, 2024

As of July 9, 2024, this outbreak is over.


As of May 6, 2024, a total of 12 confirmed E. coli O157:H7 infections have been linked to organic walnuts distributed by Gibson Farms, Inc. Seven patients have been hospitalized; two developed hemolytic uremic syndrome (HUS), a serious condition that can lead to kidney failure. No deaths have been reported. Sick people range in age from 6 to 84 years and illnesses started on dates ranging from February 1 to April 4, 2024.

Clinical Guidance

  • Presentation: Most people infected with Shiga toxin-producing E. coli experience severe stomach cramps, diarrhea (often bloody), and vomiting.
    • Symptoms usually start 3 to 4 days (range 1-10 days) after ingesting the bacteria.
    • Most people recover without treatment after 5 to 7 days.
    • Approximately 6% of individuals with confirmed E. coli O157:H7 diarrhea develop HUS 1-3 weeks after onset of diarrhea. Children under 5 years of age are at higher risk of developing HUS (15% of confirmed E. coli O157:H7 cases develop HUS). HUS presents with microangiopathic hemolytic anemia, thrombocytopenia, and acute renal dysfunction.
  • Who is at highest risk/complications: Younger children (under age 5) are at higher risk of HUS and severe complications of E. coli O157:H7 infection. The risk of developing HUS is lower in children who have a longer interval between diarrhea onset and presentation to the emergency department. More than 50% of children with HUS require dialysis, and 3% to 5% die. Patients with HUS can develop neurologic complications (eg, seizures, coma, or cerebral vessel thrombosis). Children presenting with an increased white blood cell count (>20 x 109/mL) or oliguria or anuria are at higher risk of poor outcomes, as are, seemingly paradoxically, children with hematocrit close to normal rather than low.
  • Patients should be seen by their pediatrician if they have any of these severe symptoms:
    • Diarrhea and a fever higher than 102°F (though coli O157:H7 diarrhea is often not associated with fever)
    • Diarrhea for more than 3 days that is not improving
    • Bloody diarrhea (diarrhea due to coli O157:H7 may be non-bloody initially)
    • Not tolerating oral liquids
    • Signs of dehydration, such as:
      • Decreased urine output
      • Dry mucous membranes
      • Orthostatic hypotension
    • Neurologic symptoms, particularly seizures, which may occur in the setting of HUS.
  • Diagnosis: Several US Food and Drug Administration (FDA)-cleared multiplex polymerase chain reaction (PCR) assays (usually offered as diagnostic panels) can detect a variety of enteric pathogens, including EAEC, EPEC, ETEC, and STEC, the last by detection of the genes encoding Stx1 and Stx2. Rapid immunologic assays including immunochromatography or enzyme immunoassay (EIA) may be used for detection of Shiga toxin in stool samples.
  • Precautions:
    • People who bought organic walnut halves and pieces from bulk containers should check if they are part of the recall. If they are or they are not sure, then the walnuts should be thrown away or returned to where they were purchased.
    • Advise people to wash items and surfaces that may have touched the contaminated cheese using hot soapy water or a dishwasher.
  • Treatment: Treatment is primarily supportive for all diarrhea-producing E. coli. Orally administered electrolyte-containing solutions usually are adequate to prevent or treat dehydration and electrolyte abnormalities. Antimotility agents should not be administered to children with inflammatory or bloody diarrhea. Patients with proven or suspected STEC infection should be rehydrated fully but prudently as soon as clinically feasible. Many experts advocate intravenous volume expansion during the first 4 days of proven STEC infection to maintain renal perfusion and reduce the risk of renal injury. Careful monitoring of patients with hemorrhagic colitis (including complete blood cell count with smear, blood urea nitrogen, and creatinine concentrations) is recommended to detect changes suggestive of HUS. If patients have no laboratory evidence of hemolysis, thrombocytopenia, or nephropathy 3 days after resolution of diarrhea, their risk of developing HUS is low. Most experts advise not prescribing antimicrobial therapy for children with E. coli O157 enteritis or a clinical or epidemiologic picture strongly suggestive of STEC infection.
  • Reporting: Suspected cases should be reported to a local department of public health.


Pediatric Practice Tools and Information

E coli (Escherichia coli) | E. coli | CDC

Public Health Resources

Food Safety Alert | E. coli Outbreak Linked to Organic Walnuts| CDC

Outbreak Investigation of E. coli O157:H7: Bulk Organic Walnuts | FDA

Organic Walnut Voluntary Product Recall | FDA


Infection Prevention and Control Resources

Project Firstline (


Information for Patients and Caregivers

AAP Food Poisoning and Food Contamination | In Spanish: Intoxicación y contaminación alimentaria

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