SPRINGFIELD — State health officials have traced a widespread salmonella outbreak at Subway restaurants to one Central Illinois food distributor.
But, in a final report on the incident issued Thursday, the Illinois Department of Public Health said it could not identify the exact source of the problem, which led to 109 confirmed cases and another 90-plus probable or suspect cases of the illness between late April and June.
In the 69-page report, investigators said the “most likely source” of the lettuce, tomatoes and olives linked to the illnesses was Lincoln-based Sysco Central Illinois Inc., which delivered produce to the affected restaurants.
Samples collected at the company’s distribution facility in June, after many of the victims had already contracted the illness, were tested and found negative for salmonella.
Areas that may have been the source of salmonella may have been washed down and produce that was affected may have been discarded.
“It’s hard to nail down,” said Public Health spokeswoman Melaney Arnold.
The report, which will be forwarded to the federal Centers for Disease Control, shows that 299 Subway restaurants were forced to dispose of their produce during the event.
More than 480 workers at the stores had to be tested. A dozen of them were found to be positive for the strain of salmonella.
Sangamon County had the most cases with 14, followed by Christian and Ogle counties with nine each.
In the end, 49 restaurants in 28 Central and northern Illinois counties were connected to the outbreak. More than two dozen people were hospitalized. All were discharged by mid-June.
In all, the department reported spending 4,100 hours probing the outbreak — a figure that doesn’t count time spent on the illness by local health department officials.
Representatives of Subway and Sysco could not immediately be reached for comment.