Publisher’s Platform: What you need to know about E. coli during the Walnut Outbreak

As of May 16, CDC, public health and regulatory officials in several states, and the U.S. Food and Drug Administration (FDA) are collecting different types of data to investigate a multistate outbreak of E. coli O157 infections.

Epidemiologic and traceback data show that organic walnuts distributed by Gibson Farms, Inc. may be contaminated with E. coli and may be making people sick.

Epidemiologic Data

As of April 30, 2024, 12 people infected with the outbreak strain of E. coli have been reported from 2 states (see map). Illnesses started on dates ranging from February 1, 2024, to April 4, 2024 (see timeline). Of 11 people with information available, 7 (64%) have been hospitalized. Two patients have developed hemolytic uremic syndrome, a serious condition that can cause kidney failure. No deaths have been reported.

The true number of sick people in this outbreak is likely much higher than the number reported, and the outbreak may not be limited to the states with known illnesses. This is because many people recover without medical care and are not tested for E. coli. In addition, recent illnesses may not yet be reported as it usually takes 3 to 4 weeks to determine if a sick person is part of an outbreak.

Public health officials collect many different types of information from sick people, including their age, race, ethnicity, other demographics, and the foods they ate in the week before they got sick. This information provides clues to help investigators identify the source of the outbreak.

The list below has information about sick people in this outbreak (“n” is the number of people with information available for each demographic).

• Age (n=12): Range from 6 to 84 years, Median of 57 years
• Sex (n=12): 67% female, 33% male
• Race (n=10): 90% White, 10% African American/Black
• Ethnicity (n=10): 100% non-Hispanic

State and local public health officials are interviewing people about the foods they ate in the week before they got sick. Of the 10 people interviewed, all 10 (100%) reported eating walnuts. This percentage was significantly higher than the 26% of respondents who reported eating walnuts in the FoodNet Population Survey—a survey that helps estimate how often people eat various foods linked to diarrheal illness. This difference suggests that people in this outbreak got sick from eating walnuts. Of 10 people interviewed, almost all reported buying organic walnuts from bulk bins in food co-ops or natural food stores. Investigators identified two illness subclusters of two people each who purchased bulk bin walnuts from the same store location.

Laboratory and Traceback Data

Public health investigators are using the PulseNet system to identify illnesses that may be part of this outbreak. CDC PulseNet manages a national database of DNA fingerprints of bacteria that cause foodborne illnesses. DNA fingerprinting is performed on bacteria using a method called whole genome sequencing (WGS).

WGS showed that bacteria from sick people’s samples are closely related genetically. This suggests that people in this outbreak got sick from the same food.

Traceback data collected by FDA determined that Gibson Farms, Inc was the supplier of organic walnuts sold in bulk bins at stores where ill people shopped.

Public Health Actions

Do not eat, sell or serve recalled walnuts.

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