So I feel the pain and misery of the Illinois Salmonellosis victims.
The restaurant chain ceased using onions, tomatoes, green peppers, and lettuce as a precautionary measure, but at this point the source of the microbes has yet to be discovered. Given the fact the outbreak has been traced to Subway restaurants in 28 Illinois counties, it is doubtful that this is related to Subway employees, though this did not stop Illinois health department officials from ordering thetesting of food handlers in 46 restaurants linked to the outbreak.
The microbe responsible for the outbreak is known as Salmonella serotype Hvittingfoss, and this strain is relatively rare as serotypes of Salmonella go. This also implies that a single source - probably an inventory item supplied by a vendor that the affected restaurants shared - is responsible for the outbreak.
Just an opinion from a semi-informed source: I worked in the restaurant industry for 25 years, and one of my research interests as a historian is in epidemiological history.