Explosive Diarrhea Parasite Hits 17 States Just Before Fourth of July With Michigan Cases Tripling This Year

WASHINGTON — A parasitic illness known for causing watery, sometimes explosive diarrhea has sickened hundreds of people across more than 17 states since May, with a surge in Michigan where cases have already more than tripled last year's full-season total, raising concern among public health officials heading into one of the country's most food-heavy holiday weekends.

Cyclosporiasis, caused by the parasite Cyclospora cayetanensis and commonly contracted through contaminated fresh produce, has been the focus of active investigations by the Centers for Disease Control and Prevention, the Food and Drug Administration and state health departments since the beginning of its annual warm-weather season. As of June 16, the most recent data available from the CDC's surveillance dashboard, 145 people across 17 states had contracted the infection after consuming food in the United States, with an additional 45 people who contracted the illness while traveling internationally tracked separately under a different category.

Of those 145 domestic cases, 20 people required hospitalization. No deaths were reported. The illness affected people ranging in age from 5 to 86, with a median age of 42.

Michigan's situation stands apart from the national picture. After the state recorded its first case of the season on June 22, the number of infections climbed rapidly. By July 1, the Michigan Department of Health and Human Services reported more than 170 confirmed cases in the state, a number that dwarfed the roughly 50 total cases Michigan recorded for the entire 2025 season. Those Michigan figures are not yet reflected in the CDC's national dashboard, which is updated monthly.

Asked for comment on the acceleration, the CDC was measured in its response.

"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."

In a follow-up statement provided July 2, the CDC said it did not have new national data to share and noted that the surveillance dashboard would be updated in its regular monthly cycle.

Cyclosporiasis is a parasitic infection of the small intestine transmitted through a fecal-oral route, meaning people typically become infected by consuming food or water that has been contaminated with infected fecal matter, or by touching a contaminated surface and then touching their mouths without washing their hands. The infection is not spread directly from person to person.

The most distinctive and widely recognized symptom is frequent, watery and sometimes explosive diarrhea, according to both the CDC and the Cleveland Clinic. Other symptoms can include loss of appetite, bloating, stomach cramps, gas, extreme fatigue, fever, nausea and vomiting. People generally begin experiencing symptoms anywhere from two days to two weeks after exposure, with an average incubation period of about a week. Without antibiotic treatment, the illness can persist for months and may recur in cycles of improvement followed by relapse.

The states that have reported cases so far this season include Alaska, Colorado, Connecticut, Florida, Georgia, Illinois, Louisiana, Massachusetts, Michigan, New Jersey, New York, North Carolina, Ohio, Pennsylvania, Tennessee, Texas, Virginia and Wisconsin, representing a broad geographic spread across the Midwest, South, Northeast and beyond.

Public health officials have specifically flagged the Fourth of July holiday weekend as a period of elevated risk, given the widespread outdoor gatherings, picnics and potluck meals involving fresh produce that the holiday typically brings. Fresh fruits and vegetables, including basil, raspberries, lettuce, berries, melons and cucumbers, have all been associated with past U.S. cyclosporiasis outbreaks, and warm summer conditions help explain why the illness spikes between May 1 and late August each year. Contaminated and unwashed produce is the primary transmission vehicle in the United States, where outbreaks are less common than in tropical regions of Central America, South America and Africa but still occur regularly during the warm season.

The Michigan Department of Health and Human Services previously told the Detroit Free Press that contaminated, unwashed produce tends to drive the warm-weather cases seen domestically, a pattern consistent with the national picture this year. Health officials in the state have been working to identify whether the cluster of cases there shares a common food source or exposure, but no single outbreak vehicle has been publicly confirmed.

To reduce the risk of contracting cyclosporiasis, the CDC, Cleveland Clinic and Michigan health authorities have outlined a set of practical food safety steps. They include avoiding consuming food or water that may be contaminated, including untreated water sources. Thorough handwashing with soap and water after using the bathroom and before, during and after food preparation is essential. All food preparation surfaces, cutting boards, countertops and utensils should be cleaned before and after use. Fresh produce should be washed thoroughly before eating, with firm-skinned fruits and vegetables like melons and cucumbers scrubbed well. Damaged or bruised areas on produce should be cut away before eating. Prepared fruits and vegetables should be refrigerated as soon as possible, ideally within two hours of preparation.

The infection is treatable with a specific antibiotic regimen, and most otherwise healthy individuals will recover with prompt treatment. The groups at greatest risk of more severe illness include young children, older adults and people with weakened immune systems, all of whom are advised to contact a healthcare provider promptly if they develop symptoms consistent with cyclosporiasis rather than waiting to see whether the illness resolves on its own.

No recall of any specific food product has been announced in connection with the current cases as of Thursday, and health authorities have stopped short of connecting this year's surge to any single produce item or supply chain source, describing the current situation as a surveillance-tracked seasonal increase rather than a confirmed multistate outbreak tied to a single vehicle.