NEW YORK, United States (AFP) — Americans across dozens of states have fallen victim to a microscopic foodborne parasite that can cause “explosive diarrhea,” US health authorities said.

The Midwestern state of Michigan has been at the center of the cyclosporiasis outbreak, with state authorities reporting 1,562 cases as of Friday.

The US Centers for Disease Control and Prevention said that as of Thursday 31 states had reported cases of the gastrointestinal illness, with dozens of hospitalizations but no deaths.

Health officials have not identified the cause of contamination that generally stems from fresh produce. Symptoms often lag after infection, making it difficult to pin down the source.

In the past, foods including bagged salad mixes, fresh cilantro, fresh basil, raspberries, snow peas and scallions have been linked to cyclosporiasis.

Untreated, the illness could last more than a month. It is generally not life-threatening, according to public health authorities.