SOUTH BASS ISLAND Researchers still don't know what caused illness in visitors
The cases may not be tied by location.
Hundreds of people who say they've suffered from nausea and diarrhea after traveling to a Lake Erie resort island in recent weeks, while some say they fell ill back in early June.
Others never set foot on the quaint tourist getaway, only stopping nearby.
All of these varying elements, along with the outbreak's wide scope, will make it much more difficult to find a source for the illnesses, infectious disease experts said Monday.
"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 in Toledo.
The number of gastrointestinal illnesses rose again Monday with 750 people now saying they fell ill after visiting South Bass Island and the surrounding area, which is about halfway between Toledo and Cleveland.
Researchers have identified 120 new cases since early Sunday. A week ago, health officials had documented just 78 cases.
The total includes tourists from Ontario, Canada, and 11 states as far away as California and Texas, according to the Ohio Department of Health.
So far, a handful have tested positive for two types of bacterial infections -- campylobacter and salmonella -- and one type of viral infection -- norovirus.
David Taylor, an infection control practitioner at Ohio State University Medical Center, said it was unusual that all three infections would come from the same outbreak.
"The original source is more than likely food or water that's been contaminated somewhere along the line," he said.
All three organisms could have been spread by drinking water, restaurant workers or someone who didn't wash their hands after using a restroom. Nothing has been ruled out.
It's possible that the problem may go away before investigators can pinpoint the source, Taylor said.
"Sometimes we never do find a source for it," he said. "The fact that it's a resort where people come and go makes it more difficult."
All the cases may not be linked to South Bass Island, Harrington said.
"They may be coincidental," he said. "It's possible some of those people picked up something else, somewhere else. People tend to eat out more, eat more casually in the summer. It's picnic season and tourist season."
Most people said they became sick within two or three days of visiting the summer getaway island whose main town, Put-In-Bay, draws about 15,000 people by boat on weekends to its bed-and-breakfast inns, wineries, beaches and bars. Visitors' symptoms including nausea, chills, fever, abdominal cramps, diarrhea and vomiting have generally lasted about 24 hours.
"The fast onset and fast recovery sounds more like a virus," Harrington said.
To be sure, investigators need more samples to test from people who have been ill, he said. But that won't be easy.
The state Health Department doesn't have many tests pending because most people have since recovered, agency spokesman Kristopher Weiss said.
Investigators were continuing to look for common links besides the illness and travel to the island, he said.
"It's very difficult to say where this could go," Weiss said.
Harrington said investigators should concentrate on any new cases because it will be easier to track their movements and collect samples.
"Until the organism is known, it makes the questions difficult to answer," he said. "You're really working in the dark."