SAN LUIS OBISPO, Calif. — San Luis Obispo County Public Health is wrapping up its investigation into an E. coli outbreak linked to Brookshire Farms, closing the case with five confirmed infections, ten suspect cases, and no source ever identified, health officials announced.
Read the San Luis Obispo County Public Health release: https://www.slocounty.ca.gov/departments/slo-health/public-health/department-news/slo-county-public-health-update-on-shiga-toxin-producing-e-coli-(stec)-outbreak-investigation
The Department of Public Health announced the update on November 6, 2026, according to the release.
Officials said the risk of additional exposure tied to the incident has passed, the release stated.
Five Confirmed Cases, Ten Suspect Cases, And One Matching Strain
All five people with laboratory-confirmed Shiga toxin-producing E. coli O157 infection visited Brookshire Farms on October 17 or 18, 2026, according to the investigation.
An additional ten people who visited the farm between October 16 and 26, 2026, and developed symptoms were deemed suspect cases, the release stated.
Genetic testing showed the bacterial strains in three of the patients matched each other, according to the release. A fourth test is pending, and a fifth could not be performed.
While the patient strains matched each other, they did not closely match other known strains in national databases, and the findings strongly suggest exposure to a common and unique source, officials reported.
Patient visits to the farm fell within the timeframe expected from exposure to illness, according to the release.
Negative Samples, Notable Exposures, And No Source Found
Testing of water, food, and other environmental samples collected at the farm did not find E. coli O157 specifically, according to the release.
Other types of bacteria, including other strains of E. coli, turned up in some samples, but those results did not identify the source of the outbreak, officials reported.
No additional environmental testing is planned, the release stated. Officials cited the abundance of potential sources, the absence of testable items, and delays between exposures and sampling among the limits on testing.
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Some potential exposures common to infected individuals remain notable, including edible corn cups, pumpkins, hay, and non-potable water sources, although no specific source of the E. coli O157 was identified, according to the release.
No farm animals or petting zoos, a common source of STEC, were available to the public or operating on the farm premises, officials reported.
"Based on the findings of our investigation, we believe the risk of additional exposure associated with this incident has passed, and there is no longer an ongoing public health threat," said County Health Officer Dr. Christy Mulkerin.
"Although it's frustrating to not be able to pinpoint the exact source of the infection through environmental lab testing, this is not unexpected, and bacterial contamination is often temporary and difficult to detect through available sampling methods," Dr. Mulkerin said.
No Ongoing Threat, Symptoms To Watch, And Food Safety Steps
STEC infections can cause stomach cramps, diarrhea, and sometimes bloody diarrhea, according to the release. In some cases, infection can lead to serious complications, including kidney failure.
Children under the age of 5 are at greater risk of severe complications, and community members should seek medical care if they have these symptoms, officials reported.
Health officials recommend washing hands thoroughly with soap and water after being in outdoor environments or touching animals, washing fruits and vegetables before eating them, and keeping raw foods separate from other foods during preparation and storage, according to the release.
Officials also advise avoiding untreated water and drinking only pasteurized milk and juices, and remind anyone selling or providing food to the public to follow state and County health regulations, the release stated.
Public Health cannot release additional information about the individuals affected, to protect patient privacy, according to the release.
More information about E. coli and food safety is available on the California Department of Public Health website at www.cdph.ca.gov.
Sources
County of San Luis Obispo Department of Public Health, "SLO County Public Health Update on Shiga Toxin-Producing E. coli (STEC) Outbreak Investigation," November 6, 2026: https://www.slocounty.ca.gov/departments/slo-health/public-health/department-news/slo-county-public-health-update-on-shiga-toxin-producing-e-coli-(stec)-outbreak-investigation
Transparency notes
Published: Nov 10, 2026. No major post-publication update has been logged.
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