In 2018, public health officials in California investigated an outbreak of Salmonella Thompson infections associated with chicken served at a single El Pollo Loco restaurant located on Oakdale Road in Modesto, California. A total of 49 outbreak cases were detected. Seven people were hospitalized. No one died. Illness onset dates ranged from February 15, 2018 to May 30, 2018.

Stanislaus County Environmental Health Department staff collected 73 environmental swabs from food contact and non-food contact areas at the restaurant. Salmonella Thompson was detected in 4 of the 73 samples. Three of the four S. Thompson isolates matched one of the outbreak strains isolated in ill patrons.

One employee tested positive for Salmonella Thompson. The affected employee was treated and cleared by retesting before returning to work. The employee was considered to be a victim of the outbreak.

Evidence collected during the investigation suggested that cross-contamination or inadequate cooking of chicken may have resulted in illness to customers and a single employee.