Health department officials eventually identified 109 confirmed cases of Salmonella Hvttingfoss among Subway customers. Isolates from 107 cases had identical PFGE patterns, and two had closely related patterns. Onsets of illness were from April 25 through June 20, 2010. Individuals determined to be confirmed cases reported eating at 49 individual Subway restaurants in Illinois between May 5 and June 4, 2010 and 96% of cases reported eating at a Subway location within the distribution area of one Subway product distributor. Additionally, of those infected with Salmonella Hvittingfoss, twelve individuals were food handlers of the Subway restaurant chain who worked at different locations.
No individual food was ever determined to be the source of the 2010 Salmonella outbreak among Illinois Subway customers.