Officials are looking into canned fruits and vegetables as well as pasta and potatoes salads and other menu items, according to Ohio Department of Health spokeswoman Shannon Libby.
So, you may be wondering how to keep your pantry safe in time for picnic season.
Here's what you need to know:
What is botulism?
"All forms of botulism can be fatal and are considered medical emergencies," according to the CDC. "Foodborne botulism is a public health emergency because many people can be poisoned by eating a contaminated food."
How common is it?
"Botulism has virtually been eliminated in this country," said Dr. William Schaffner, chairman of preventive medicine at Vanderbilt University Medical Center in Nashville, Tennessee.
There are about 145 cases a year in the U.S., according to the CDC. Only 15 percent of those are foodborne. The rest are either wound-related because botulism lives in the dirt, or something called infant botulism, in which babies with no botulism antibodies somehow consume a small amount of the spores, said Dr. Frank Esper, an infectious diseases expert at UH Case Medical Center in Cleveland, Ohio.
"It's why we're not allowed to give honey to children under 1 year of age," Esper said. "A small amount of botulism can be found there."
He said most people have some resistance to botulism in small amounts, but infants have no antibodies.
Why is it found in canned goods?
"Back in the day when there was a lot of home-canning, people didn't always meticulously follow protocols," Schaffner said. "The spores were not killed and given that this was now an environment in a sealed container, the bacteria could multiply and produce the toxin."
With the advent of commercial canning and better understanding of botulism to put food safety procedures in place, he said it's now rare to have a canned good-related botulism outbreak.
What can you do to stay safe?
Unless the Ohio potluck investigators find that the food that caused the illness was commercially canned, Schaffner said people have nothing to worry about. But if they see a can that is puffy or dented, discard it.
"Spoilage of one kind or another likely occurred," he said. "There's no reason to subject yourself to any kind of chance of getting sick."