At least eight of the sick people were contaminated with the same strain of the bacteria.
In total, ten area cases of E. Coli are now confirmed, and that's making some people nervous.
"It's a little frightening I guess, " said former healthcare worker Pat Murray of Mount Morris.
"It makes you stop and think about everyplace you eat and everyplace you go."
In more than 3 decades as Public Health Director, Joan Ellison has never seen an E. Coli outbreak of this size.
The patients range in age from 10 to 75.
She says all of the cases have been traced back to Livingston County, but their source is still a mystery.
"The way I'm describing it is there's a thread that ties all these people together but there's not a rope that makes it strong," said Ellison. "So we can't implicate one thing, be it a food, facility or person. That's missing. That's the missing link."
Undercooked meat and unpasteurized milk or juice are common sources of E. Coli contamination.
County investigators continue to interview patients to find out if any have eaten at the same restaurant or shopped at the same supermarket.
The team of 7 is frustrated that they cant get to the bottom of the issue.
Ellison added "One case here, one case 5 days later, one case 5 days later. Usually they're clustered."
Pat Murray wants investigators to find the source soon, but in the meantime hopes those who handle her food are extremely careful.
"I think everybody's pretty contientious about it, restaurants especially. They certainly observe good hygiene I'm sure, in most instances. You would hope."
Symptoms include severe diarrhea and abdominal cramps, and could be deadly for the very young and the elderly.
If you think you may be sick, you're asked to call your county health department.