Four people contracted severe E. coli infections after eating lettuce from a Wendy’s restaurant in North Ogden, according to the Standard-Examiner.

Two of the four cases were traced to a CORE Academy conference held at Orion Junior High School in Harrisville and catered by Wendy’s. A third case was determined to have been a secondary infection from one of the first two patients.

The fourth case was an individual who ate at the Wendy’s for three straight days during that same time period. Three of the four infected have developed into hemolytic uremic syndrome, a potentially fatal kidney disease.

At least 300 more people were potentially exposed to the infection while attending the conference but health officials don’t believe any more infections will occur.

The only common food item shared was iceberg lettuce from Wendy’s.

"We believe that the source of this food-borne contamination was limited to this one Wendy’s restaurant," House said.

"A main head of lettuce could be the culprit of the whole problem," said Glenn Kinney, regional epidemiologist for the Utah Department of Health.