Beginning in August 2017, a prolonged outbreak of Salmonella Heidelberg infections occurred among patrons of two chain restaurants with common ownership. Both restaurants were located in Bemidji, Minnesota. Thirty-six confirmed cases and 10 probable cases were identified. Onset dates ranged from August 12 to December 8, 2017. Nine cases were hospitalized. One person died.

Initially, illnesses were only associated with the "north" location. Health officials analyzed food consumption of 12 confirmed cases who dined at this location with meal dates before September 22. The 12 cases provided a probable list of foods eaten. All reported eating food with a beef patty. Receipts from September 1 were used in a case-control analysis. In this analysis. beef patties (12 of 12 cases vs. 365 of 545 controls; odds ration [OR], undefined; p=0.012) along with condiments only served on beef patties were associated with illness.

All 36 employees at the north location were interviewed on September 22. Twelve reported recent gastrointestinal illness or fever. Thirty-one employees submitted at least one stool specimen. Of these, 5 were positive for the outbreak strain of Salmonella Heidelberg.

New cases with laboratory confirmed Salmonella Heidelberg continued to occur in October, November and December. Patrons had consumed food from both the south and north locations. The Minnesota Department of Agriculture performed food product testing and collected environmental sampling. All samples were negative for Salmonella. Ongoing employee illness screening continued through January 9, 2018.

Multiple positive food workers, and possible opportunities for cross-contamination by food workers facilitated by improper handwashing and glove use, were identified and explain the duration of the outbreak.