At least 29 people have fallen ill during a fast-moving E. coli outbreak in Michigan and Ohio, while the source of the outbreak is still unknown.

Of the confirmed cases, 15 are in Michigan and 14 are in Ohio. No deaths have been reported from the outbreak, but at least nine people have been hospitalized.

The Centers for Disease Control and Prevention said that those numbers are likely undercounted and that "the true number of sick people in this outbreak is likely higher."

The CDC is asking for help in finding the source of the outbreak. If you're experiencing E. coli symptoms, you should write down everything you ate in the week before becoming sick and report your illness to your local health department.

This outbreak is larger than the usual summer uptick

Symptoms of E. coli sickness vary from person to person but often include severe stomach cramps, diarrhea that is often bloody, vomiting and a fever. These symptoms usually start within three to four days after the bacteria is swallowed, the CDC said, and most people recover without treatment within a week.

While the source of the current outbreak is unknown, some of the cases have been linked to each other through laboratory testing and results, the Michigan Department of Health and Human Services said.

Michigan has seen a jump in E. coli infections compared to this same time last year. At least 98 cases have been recorded this August compared to 20 cases in the same time period last year.

"While reports of E. coli illness typically increase during the warmer summer months, this significant jump in cases is alarming," Dr. Natasha Bagdasarian, MDHHS chief medical executive, said in a statement. "This is a reminder to make sure to follow best practices when it comes to hand hygiene and food handling to prevent these kinds of foodborne illness."

The CDC offers tips on how to avoid E. coli infections

To help prevent E. coli infections, the CDC recommends keeping things clean. This includes washing your hands often, washing surfaces and utensils, and rinsing produce before eating or preparing it.

Separating things like raw meats from foods that won't be cooked also helps lessen the chance for contamination.

Temperature is also important. Ensuring your meats are cooked to a high enough temperature helps kill germs, the CDC said. Keeping perishable food refrigerated or making sure it gets back in the fridge within two hours is also a good prevention practice.