Nearly 1,000 people in the U.S. state of Michigan have been infected with a parasite capable of causing weeks of watery diarrhea, marking the largest outbreak of its kind in the state’s history and one of the biggest in the United States in recent years.
So far, no deaths have been reported, and the source of the Cyclospora parasite infection has not yet been identified. At the same time, investigations into similar illnesses are underway in 28 other U.S. states, including Ohio, where cases have also been reported among residents living near the Michigan border.
Michigan authorities first announced the outbreak last week, when they were aware of more than 170 cases recorded since June 22, all in the southeastern part of the state. Michigan typically records only about 50 cases throughout an entire year, according to the Associated Press.
On Wednesday, state officials announced that the number of confirmed cases had risen to 992, including around 40 hospitalized patients. Just across the state border, Lucas County, Ohio, had reported 306 cases as of Wednesday. More than 500 cases have been recorded across northwestern Ohio.
Sudden spikes in Cyclospora infections can be extremely difficult to investigate, and identifying the source of foodborne contamination often presents a major challenge. Nevertheless, “it is clear that a connected outbreak is currently underway,” Dr. Natasha Bagdasarian, Michigan’s chief medical executive, told the AP.
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What Is Cyclospora?
Cyclospora is a microscopic, spherical parasite that most commonly causes watery diarrhea “with frequent and sometimes explosive bowel movements,” according to the U.S. Centers for Disease Control and Prevention (CDC). The illness it causes is known as cyclosporiasis. It is generally not life-threatening and is most often treated with antibiotics. Outbreaks typically occur during late spring and summer.
The parasite, which thrives in warmer conditions, infects the intestines and spreads through fecal contamination. In previous outbreaks, people became infected after consuming fruits or vegetables exposed to irrigation water contaminated with feces.
Cyclospora is less common than many other foodborne pathogens, such as Salmonella or Escherichia coli (E. coli). For years, only a handful of outbreaks were reported annually in the United States, but the number of cases began increasing about a decade ago, with particularly sharp spikes in 2018 and 2019. Experts attribute the rise to climate change as well as improved methods of detecting the infection.
Over the past 20 years, only a small number of documented outbreaks have exceeded 1,000 cases.
That short list includes the 1997 outbreak linked to raspberries imported from Guatemala, which infected more than 1,000 people in the United States and Canada, as well as the 2019 outbreak linked to basil imported from Mexico, during which more than 2,400 people became ill.
There's a parasite spreading through the US right now that you cannot wash off your food, cannot catch from another person, and will not feel for a full week after you've already eaten it.
— Aakash Gupta (@aakashgupta) July 12, 2026
Michigan alone has close to 1,000 confirmed cases. It's called Cyclospora, and almost… https://t.co/ZYEQAhUyiS
What Is the Current Situation?
The number of cases appears to be rising rapidly in southeastern Michigan and surrounding areas. However, the situation is not currently considered a national public health emergency.
There is no evidence that the parasite has evolved to become more contagious, said Diana Blau, acting chief of the CDC’s Division of Parasitic Diseases.
Thousands of cases of cyclosporiasis are reported in the United States every year, so it is still unclear how unusual this year’s outbreak will ultimately prove to be, she added. However, according to the CDC’s latest national data, the number of reported cases so far is four times higher than during the same period last year, although those national figures significantly lag behind the reports released by individual states.
Michigan appears to be the hardest-hit state, but Bagdasarian believes that “part of the reason everything looks like a Michigan problem” is that the state is conducting particularly intensive investigations and reporting of cases.
How Can You Protect Yourself From Cyclospora?
Health authorities recommend that anyone experiencing diarrhea that does not resolve on its own within a few days should consult a doctor and discuss the possibility that Cyclospora infection may be the cause.
The best way to protect yourself is to avoid food or water that may be contaminated with the parasite.
Fresh fruits and vegetables should be thoroughly washed before consumption. However, it should be noted that Cyclospora can adhere very firmly to certain foods, meaning that washing alone may not completely eliminate the risk of infection.
While the investigation into the possible source of the outbreak continues, Michigan authorities are advising consumers to buy whole heads of lettuce instead of pre-washed bagged lettuce or ready-made salad mixes. They also recommend removing the outer two to three leaves before thoroughly washing the remaining leaves under running water.
Whenever possible, vegetables should also be cooked before consumption.
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Source: Euronews; Foto: Pexels