An outbreak of diarrhea caused by the parasite cyclospora has risen to more than 3,000 cases in Michigan and Ohio.

As state health officials scramble to find the source of the foodborne parasite, the CDC said Friday it’s unclear whether the outbreaks across the country are connected.

The outbreak is the largest in Michigan’s history, with more seen across the country.

A widespread parasite outbreak in the US causes diarrhea, affecting 31 states; learn about symptoms, transmission, and prevention.