Several factors hampered investigators’ efforts to determine where the E. coli O157 outbreak originated, said Bill Wharton, spokesman for Public Health – Dayton & Montgomery County. The investigation is finished, he said.

“This was an extensive investigation that involved many segments of our department,” Wharton said. “It was as thorough and as complete an investigation as we’ve ever done.”

The outbreak was linked to a July 3 customer appreciation picnic at Neff’s Lawn Care in German Twp. More than 300 people attended the event, and many carried in food to share.

A statistical analysis of data from 117 interviews of people who attended and ate at the picnic did not conclusively link any of the meat items served to the outbreak, investigators said.