In May 2018, Public Health Seattle and King County (PHSKC) officials investigated an outbreak of Shiga toxin-producing E. coli(STEC) associated with three Homegrown restaurants. The results of the investigation implicated pesto used exclusively on the chicken pesto sandwich.

Four people tested positive for STEC O26 after consuming food from three different Homegrown restaurants in King County. Symptoms included abdominal cramps and diarrhea, with one person reporting bloody diarrhea. All four ate the chicken pesto sandwich from one of the following locations: Redmond, Kirkland or Seattle (Westlake Ave). Of the four ill persons, three were adults and one was a child. Illness onsets occurred during April 24–May 6, 2018. Meal dates occurred during April 24–26, 2018.

On May 24, 2018, PHSKC Environmental Health investigators visited the three Homegrown locations where the ill people reported eating. During the field inspections, potential risk factors, including handwashing facilities violations at two of the three locations, and a cold holding temperature violation at one of the three locations, were identified and discussed with the restaurant managers. PHSKC did not identify any employees who experienced similar symptoms before or after meal dates for the ill customer.

The various ingredients of the chicken pesto sandwich were also investigated. All Homegrown locations in King County stopped selling this particular sandwich while the investigation was ongoing. The three restaurants under investigation were required to complete a thorough cleaning and disinfection. No employees reported working at Homegrown while experiencing illness in the three weeks prior to the illness onset dates of the customers who got sick. Investigators also reviewed the requirement that restaurant employees are not allowed to work while having vomiting or diarrhea.

Three of the four people who got sick, tested positive for STEC O26 with the same genetic fingerprint, suggesting that they have a common source of infection; genetic fingerprinting for the other ill person could not be completed. Pesto from each location tested negative for STEC O26.[1]