Lettuce or salad greens could be the source of Michigan’s outbreak of cyclosporiasis, an infection characterized by intense diarrhea, state health officials said Monday.

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“Early information has shown lettuce as a common product that regularly comes up during the investigation,” Dr. Natasha Bagdasarian, the state’s chief medical executive, said in a statement.

There is not enough information to pinpoint the type of produce, the grower or the supplier, and other food items cannot be ruled out, the state Department of Health and Human Services said in the same statement.

The finding applies only to Michigan, which has had the lion’s share of cases so far: 2,640. Total cases number near 3,000 for the foodborne gastrointestinal illness, which has shown up in 31 states as part of a national outbreak, according to the Centers for Disease Control and Prevention.

The CDC said 86 people have been hospitalized. The numbers often lag behind, however, as it can take a week for symptoms to appear, health experts say.

The parasitic illness can cause flu-like symptoms, including severe fatigue and body aches, and evolve with watery diarrhea that is sometimes uncontrollable.

People may also have unusually bad gas, stomach cramps and nausea. One of the most serious issues can be dehydration. It can be treated with fluids and an antibiotic.

Michigan health officials urged consumers to avoid prepackaged salads and opt for individual heads of lettuce that should be rinsed thoroughly. Outer layers should be discarded, they said, and vegetables should be cooked when possible.