The wide scope of an outbreak that sickened hundreds of travelers to a Lake Erie resort island will make it difficult to find a source for the illness, infectious disease experts said.
Some say they suffered nausea and diarrhea after traveling to South Bass Island in recent weeks, while some say they fell ill in early June.
Others never set foot on the quaint tourist getaway, only stopping nearby.
"It's not like you have 600 people who went to the same wedding, and they all had the coleslaw," said Brian Harrington, a professor of public health at the Medical College of Ohio.
The number of gastrointestinal illnesses rose again on Monday, with 750 people now saying they fell ill after visiting the island and the surrounding area. The island is about halfway between Toledo and Cleveland.