U.S. health officials are investigating a rising number of cases of cyclosporiasis, an intestinal illness caused by the microscopic parasite Cyclospora cayetanensis, and are searching for a contaminated food source, according to the Centers for Disease Control and Prevention and news reports.
The CDC's surveillance summary counted 145 cases acquired in the United States from May 1 through June 16, 2026, across 17 states, with 20 people hospitalized and no deaths. The agency said patients ranged in age from 5 to 86, with a median age of 42, and that 61% were female. The Guardian reported a broader tally of more than 400 cases across 18 states; the CDC's 145 figure covers only the period from May 1 to June 16.
The most commonly reported symptom is watery diarrhea with frequent, sometimes explosive, bowel movements, according to the CDC. The agency says cyclosporiasis can also cause loss of appetite, cramping, nausea and fatigue, and that the illness can last for weeks if untreated.
A separate surge in Michigan
One of the largest clusters is in Michigan. The state's Department of Health and Human Services reported an outbreak, and more than 170 cases have been reported in southeastern Michigan since June 22, according to the Michigan health department and the CDC. Officials have not yet publicly identified a single food linked to the Michigan cases.
The CDC has emphasized that the national numbers do not necessarily represent one connected event. "There is currently no evidence of a single, multistate Cyclospora outbreak linking all cases," the agency said in its surveillance summary, adding that the total reflects multiple clusters under investigation by the Food and Drug Administration along with unlinked cases.
How cyclospora spreads, and past outbreaks
Cyclospora spreads when people consume food or water contaminated with feces containing the parasite, and it is not passed directly from person to person, according to the CDC. In the United States, outbreaks have historically been linked to fresh produce, including raspberries, basil, cilantro, snow peas and mesclun lettuce.
The illness follows a seasonal pattern, with U.S. cases concentrated from May through August and peaking in June and July, the CDC says. Larger episodes have occurred before: federal case notes recorded multiple cyclosporiasis outbreaks in 2018 in which at least 160 people were hospitalized, and a 1996 outbreak tied to imported raspberries produced roughly 1,465 cases across the United States and Canada, according to public-health literature.
Treatment and what to watch
Cyclosporiasis is treatable. The CDC says the standard therapy is the antibiotic combination trimethoprim-sulfamethoxazole, sold under names including Bactrim and Septra, and describes it as highly effective. The agency advises washing fresh produce, while noting that washing may not fully remove the parasite.
The central open question is the source. The CDC and FDA are continuing to trace where any contaminated produce originated, which could lead to recalls or import actions. The CDC's cyclosporiasis surveillance season runs through August 31, meaning additional cases may still be reported.