‘Explosive’ diarrhea illness reported across US. See map of affected states

You may want to be extra cautious with your fresh fruit and veggie platter this holiday weekend: An explosive diarrhea-causing parasite is behind a surge of summer food poisoning cases right before Independence Day.

Cyclosporiasis, a stomach-churning illness caused by a parasite often found on produce, has sickened hundreds across more than 17 U.S. states since May 1, according to the Centers for Disease Control and Prevention (CDC) and state health data. One state, Michigan, is contending with a cluster of infections that has already more than tripled its total case count compared with 2025.

While state health authorities, the CDC and the Food and Drug Administration (FDA) are working to determine a common thread among the illnesses, a singularly related outbreak hasn't been identified. Instead, the cases thus far appear to be part of a seasonal surge, though officials are searching for a potential throughline.

"CDC has no evidence of a single, multistate Cyclospora outbreak linking cases happening right now and being reported in press," the agency said in a June 2 statement to USA TODAY. "The data currently found on CDC’s website is a surveillance count of cases across the United States of people with cyclosporiasis. This number includes clusters of cases currently under investigation by FDA and cases that have not been linked to a common source."

Here's what to know about avoiding the parasitic infection while picnicking this Fourth of July and beyond, including where it's been detected so far.

What is cyclosporiasis? What are the symptoms?

Cyclosporiasis is a parasitic infection that causes unpleasant gastrointestinal symptoms often associated with food poisoning, such as diarrhea, nausea and vomiting. It is caused by the parasite Cyclospora cayetanensis, also known simply as cyclospora, and is usually contracted through contaminated food.

The most common symptom is watery, frequent and sometimes "explosive" diarrhea, according to the CDC and Cleveland Clinic, though other stomach troubles can include:

• Loss of appetite
• Bloating, including burping and gas, or stomach cramps
• Extreme tiredness (fatigue)
• Fever
• Nausea
• Vomiting

See states with cyclosporiasis cases

The CDC tracks cases of cyclosporiasis based on where they were contracted. As of June 16, 145 people across 17 states had contracted the infection after eating food in the United States. An additional 45 people, who are tracked and categorized separately, contracted it while traveling abroad.

Of the 145 who became ill in the U.S., 20 were hospitalized and none died. Cases occurred in people ages 5 to 86, with the median age 42. The cyclosporiasis "season," or the months during which the U.S. typically sees a spike in the illness, begins May 1 and lasts through the end of August, according to the CDC.

These numbers do not, however, include the more than 150 people who have become ill in Michigan after the first case was discovered in the state on June 22. On July 1, the state's health department said "more than 170 cases" had been reported, a significant spike from last year's statewide total of about 50.

The CDC told USA TODAY in a July 2 statement that it did not have new data to provide and that the surveillance dashboard for cyclosporiasis infections is updated monthly. The map below reflects the latest available CDC data as of June 16, and additional state-level reporting as of June 30.

• Alaska
• Colorado
• Connecticut
• Florida
• Georgia
• Illinois
• Louisiana
• Massachusetts
• Michigan
• New Jersey
• New York
• North Carolina
• Ohio
• Pennsylvania
• Tennessee
• Texas
• Virginia
• Wisconsin

How to avoid catching a diarrhea-causing parasite 

Cyclosporiasis is transmitted via a fecal-oral route, meaning contact with foods, drinks and surfaces contaminated with infected poop particles. Usually, this means consuming the affected food or drink directly, or touching something contaminated and then touching your mouth without washing your hands.

We often see a spike in cyclosporiasis infections during warm summer months, as infected fecal matter makes its way onto fresh, summery produce, including basil, raspberries and lettuce, which have all been associated with past U.S. outbreaks, according to the CDC.

While outbreaks are more common in tropical or subtropical parts of the world, such as Central America, South America and Africa, contaminated and unwashed produce tend to lead the warm-weather spikes in the States, Michigan Department of Health and Human Services previously told the Detroit Free Press, part of the USA TODAY network.

People typically become sick about a week after exposure, though symptoms can appear in as little as two days and as much as two weeks later.

The infection is treated with antibiotics, and while most healthy people can probably fight it off on their own, prolonged, untreated illness can last for months and recur, according to the CDC. As is often the case, children, older people and those with compromised immune systems are more likely to become severely ill or even die, and should contact a health care professional if they become sick.

To prevent catching cyclosporiasis in the first place, the CDC, Cleveland Clinic and Michigan Health Department suggest that you:

• Avoid consuming food or water that may be contaminated with feces. Avoid drinking or cooking with untreated water.
• Wash your hands with soap and water after using the bathroom and before, during and after food prep.
• Wash all food prep surfaces, including utensils, cutting boards and countertops, before and after use.
• Wash and peel vegetables before eating them; scrub produce with skins like melons and cucumbers well; and cut away damaged or bruised areas on fruits and vegetables before preparing and eating them.
• Refrigerate prepared fruits and vegetables as soon as possible (within two hours). 

Contributing: Kristen Jordan Shamus, Detroit Free Press; Sara Moniuszko, USA TODAY