A parasite causing diarrhea is spreading in U.S. as officials investigate
As of July 1, the CDC reported 145 cases of cyclosporiasis across 17 states from May 1 through June 16, with 20 people being hospitalized.
The U.S. Centers for Disease Control and Prevention (CDC) is investigating as a parasite that causes watery diarrhea appears to be spreading just as summer hits its stride.
The CDC earlier this week said it’s looking into an uptick in cyclosporiasis, with the state of Michigan reporting a surge in cases. As of July 1, the CDC reported 145 cases of cyclosporiasis being acquired across 17 states from May 1 through June 16, with 20 people being hospitalized as a result. Those impacted range from age five to 86.
The Michigan Department of Health and Human Services also stated on July 1 that it is “actively investigating a large and growing outbreak of cyclosporiasis.”
“As of Tuesday, June 30, more than 170 cases have been reported in Monroe, Lenawee, Washtenaw, Wayne, Livingston, Shiawassee and Jackson counties in the past nine days,” the news release states. “Typically, Michigan only identifies around 50 cyclosporiasis cases per year.”
According to the Public Health Agency of Canada (PHAC), cyclosporiasis is an illness of the intestines caused by a parasite called cyclospora. The most common way that cyclospora is spread is by “eating food or drinking water that contains the cyclospora parasite.”
“The cyclospora parasite gets in sources of water when feces from infected people enter the water supply,” PHAC states. “Food can then become contaminated when this water is used on crops” and “in food processing and packaging.”
In addition, foods can become contaminated from infected farm workers or food handlers.
This can happen when proper sanitation techniques, such as hand washing, wearing gloves or any other barriers or avoidance of cross-contamination, are not implemented.
Cyclospora can also be found in sewage and untreated water.
The CDC identifies the cyclosporiasis season to be from May 1 through to Aug. 31.
When contaminated food or water is consumed, it may take seven to 14 days for symptoms to appear.
If left untreated, symptoms can persist for a few days up to a few months. Most people have symptoms for six to seven weeks but in other cases, symptoms can come and go.
Cyclospora can be found worldwide, according to PHAC, but is most commonly found in tropical and subtropical areas such as:
The Public Health Agency of Canada confirmed to Global News that the agency is not currently investigating any outbreaks in Canada.
Between 2004 and 2019, an average of 238 cases of cyclosporiasis were reported through the Notifiable Disease Surveillance System.
However, a September 2025 research article investigated a total of 5,337 Canadian cases between 2000 and 2022, where adults aged 30 to 59 were “disproportionately affected.”
Although the PHAC states cyclospora “is not common on food and is not in drinking water in Canada,” the agency also says that “food can be a source of cyclosporiasis for Canadians when imported from countries where cyclospora is common” and “can be hard to prevent.”
Basil, cilantro, raspberries, blackberries, Mesclun lettuce, snow and snap peas, and pre-packaged salad mixes are some of the imported foods that have been linked to the parasite.
Canadians at the greatest risk of developing cyclosporiasis are travellers to high-risk countries who either eat fresh produce or drink untreated water, while young children, older adults and those with a weakened immune system are at higher risk for longer, more severe illnesses.