By Brenda Goodman, CNN

(CNN) — This July 4th weekend, you may want to give those raw berries or green salad the side-eye.

That’s because a parasite that can contaminate raw produce and causes ferocious and long-lasting bouts of diarrheal illness is making people sick across several states.

Nationwide, 145 cases were reported by 17 states between May 1 and June 16, according to the US Centers for Disease Control and Prevention. At least 20 of those have been hospitalized, according to the CDC.

The agency says it’s typical for case counts to rise in the summer, and several states are reporting an unusually sharp jump in cases.

Michigan, which typically identifies around 50 cases of cyclosporiasis in a year, has reported at least 170 cases, clustered in 7 counties, over the past nine days, according to the state’s Department of Health. The state’s numbers do not appear to be included in the CDC’s count.

Since May 1, New York State, excluding New York City, has seen 107 cases in the state, and typically logs 500-700 cases statewide each year, according to the New York State Department of Health.

Federal and state health officials say there is currently no evidence of a single, multistate cyclospora outbreak linking all cases. Investigations to identify potential clusters and sources of illness are ongoing.

Cyclosporiasis is caused by a single-cell parasite that’s carried in human feces. It gets into food when water contaminated with feces is sprayed on crops. Once on plants, in the humid environment of a farm field, it begins to multiply, said Dr. David Freeman, professor emeritus of infectious diseases at the University of Alabama at Birmingham. It can often be a problem for travelers, though the CDC says the cases currently under investigation did not report travel in the two weeks before they got sick.

Though no specific food has been implicated in the current outbreaks, Freeman said there are two categories of produce that seem to turn up often as the source of outbreaks: What Freeman calls the ‘basil and herb’ category “cilantro, basil, you know, plants that grow, and that you might put, in a salad or use as a garnish,” he said and the fresh berry category, which he describes as “strawberries, blueberries, melons, things that grow in fields.”

The parasite is killed by heat, so cooking normally takes care of it, but when the weather warms up and people look for ways to leave their stoves off, this stomach-churning bug finds an opening.

To keep from getting sick, it’s important to thoroughly wash all fresh produce before eating it.

“Just the act of washing it with a lot of water is certainly going to get the organisms off of there,” Freeman said.

Thoroughly washing hands and kitchen counters, and cutting surfaces, is important, too.

But be aware, Freeman said, that bleach doesn’t kill it. So Clorox wipes used on the go or at a picnic won’t do the trick. Instead, thorough handwashing with soap and water and a follow-up with an alcohol-based hand sanitizer are safer bets.

Freeman says the primary symptoms are frequent bouts of watery diarrhea, loss of appetite, and a low-grade fever, and these can start anywhere from 2 to 14 days after eating contaminated food.

Staying hydrated and replenishing electrolytes with a drink like Gatorade or Pedialyte is important, he added.

“If you’re having really bad diarrhea and you’re having some fever, I would probably seek medical help right away,” Freeman said.

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