As officials track a foodborne parasite tied to explosive diarrhea, answers remain elusive


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State and federal health officials are investigating a rise in cases of cyclosporiasis, a foodborne parasitic illness that can cause severe, sometimes explosive diarrhea. 

The CDC has identified 145 cases across 17 states among people who became infected in the U.S. between May 1 and June 16, along with 45 infections linked to recent international travel. Twenty people have been hospitalized, but no deaths have been reported. Patients range in age from 5 to 86 years old. 

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Those national figures do not yet include Michigan’s rapidly growing outbreak. The state’s Department of Health and Human Services reported Wednesday that more than 170 cases were identified in nine days across several counties, far exceeding the state’s typical annual total of roughly 50 cases. That nine-day period began nearly a week after the CDC published its June 16 case count. Investigators are working to determine whether patients share a common source of exposure. 

Although the cyclosporiasis cases have drawn widespread attention, the parasite is not a new public health concern. Infections occur every year across the country and typically rise between May and August as Americans eat more fresh produce. However, the number of reported cases has risen substantially over the past decade, climbing from fewer than 600 cases in 2016 to more than 4,700 in 2019, according to CDC data

While earlier U.S. cases were most often linked to international travel or imported produce, investigators have increasingly identified the parasite on domestically grown produce in recent years. Last year, the CDC recorded more than 1,000 locally acquired cases.

What is cyclosporiasis?

Cyclosporiasis is an intestinal illness caused by the Cyclospora parasite. People typically become infected after consuming contaminated water or food, namely fresh produce. 

Unlike many other gastrointestinal illnesses, cyclospora is generally not spread directly from person to person,because the parasite must mature in the environment for several days to weeks before it can infect someone else.

Symptoms usually begin about a week after exposure and commonly include watery diarrhea, abdominal cramping, bloating, nausea, fatigue, loss of appetite and weight loss. Some patients describe the diarrhea as sudden or explosive. 

The illness is rarely life-threatening, and can be treated with antibiotics. However, symptoms can persist for weeks or even relapse if left untreated. Though cyclospora infections are relatively uncommon in the U.S., the parasite is endemic in many tropical, developing countries around the world. 

Elusive sources

Health officials have not yet identified the source of the current illnesses. The Food and Drug Administration (FDA) is working with the CDC and state health departments to interview patients, trace where they purchased food and collect samples as investigators search for a common source. 

At this time, officials say there is no evidence that all reported illnesses stem from a single contaminated food. Instead, the CDC said it is investigating several clusters occurring simultaneously in multiple states and other sporadic cases that may be unrelated.

Historically, U.S. outbreaks have been linked to fresh produce including cilantro, basil, leafy greens, salad mixes and berries. But unlike many foodborne outbreaks, cyclosporiasis investigations often end without a definitive answer. 

One reason is timing. Symptoms typically do not appear until about a week after someone eats contaminated food. By then, patients may struggle to remember exactly what they ate, grocery receipts may be gone, and leftovers may have been discarded and no longer available for testing. 

Health officials recommend washing fresh fruits and vegetables, practicing good hand hygiene and seeking medical care if diarrhea persists for several days or is accompanied by severe dehydration. 


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Why this story matters

A multistate rise in cyclosporiasis cases, including a rapidly growing outbreak in Michigan, means Americans eating fresh produce this summer face a documented increase in exposure risk from a parasitic illness that can cause prolonged, severe gastrointestinal symptoms.

No food source identified yet

The CDC says there is no evidence all current illnesses share a single contaminated food, and investigators are simultaneously tracking multiple clusters across states alongside unrelated sporadic cases.

Symptoms can last weeks

Without antibiotic treatment, cyclosporiasis symptoms, including watery diarrhea, cramping and fatigue, can persist for weeks or relapse, according to the CDC.

Fresh produce is the common link

Historically U.S. outbreaks have been tied to cilantro, basil, leafy greens, salad mixes and berries, and officials recommend washing all fresh fruits and vegetables and seeking care if diarrhea persists.

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Fear No Fact.

Don't just take our word for it.


Center-rated reporting

According to media bias experts at AllSides

AllSides Center-rated reporting May 2026

Transparent and credible

Awarded a perfect reliability rating from NewsGuard

100/100

Welcome back to trustworthy journalism.

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Bias comparison

  • Media outlets on the left frame the outbreak as a public-health and food-safety alert, leaning on dramatic terms like “explosive diarrhea” and “mystery” while emphasizing CDC findings that cases were domestically acquired.
  • Media outlets in the center stay more restrained, stressing cases, counties, and advice on fresh produce.
  • Media outlets on the right turn the same story into a crisis narrative, using “foreign,” “infiltrates,” “panic,” and “scramble” to cast the parasite as an outside threat.

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Key points from the Left

  • The Centers for Disease Control and Prevention is investigating an outbreak of cyclosporiasis caused by the parasite Cyclospora cayetanensis, with 145 cases across 17 U.S. States reported between May 1 and June 16, 2026, including 20 hospitalizations and no deaths reported.
  • Most patients, aged 5 to 86, became sick after consuming contaminated food within the U.S. Without recent international travel, suggesting domestic food sources are responsible.
  • Symptoms include prolonged watery diarrhea, abdominal cramps, fatigue, nausea, and loss of appetite, with the infection potentially lasting over a month and often resolving without treatment in healthy individuals.
  • The CDC and FDA are investigating multiple clusters without identifying a specific contaminated food source, as Cyclospora spreads through contaminated produce and resists routine washing, complicating traceback efforts.

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Key points from the Center

  • Federal health officials are investigating a Cyclospora parasite outbreak that has sickened 145 people across 17 states, with patients reporting no recent international travel suggesting domestic food contamination.
  • Cyclosporiasis, a nationally notifiable intestinal illness, typically surges during spring and summer, with the CDC defining the season as running through Aug 31.
  • Patients range in age from 5 to 86 with a median age of 42; 61 percent are female, and Twenty individuals have required hospitalization with no deaths reported.
  • Public health authorities, including the CDC and FDA, are investigating clusters across multiple states, emphasizing no evidence of person-to-person spread and pointing toward contaminated food sources.
  • To reduce illness risk, the CDC recommends washing hands and scrubbing produce under running water, while officials suspect the true infection count exceeds the 145 reported cases.

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Key points from the Right

  • At least 145 people across 20 US states have been infected by the parasite Cyclospora cayetanensis between May and June 16, with 20 hospitalizations and no deaths reported.
  • New York has the highest number of cases, followed by Texas and Illinois, with other affected states including New Jersey, Florida, and Washington, DC.
  • Officials believe the outbreak is linked to contaminated food consumed within the United States, as no patients reported recent international travel; investigations into the exact food source are ongoing.
  • Symptoms of cyclosporiasis include severe watery diarrhea, stomach cramps, and fatigue, often starting about a week after exposure; the illness may last weeks or months if untreated and typically requires treatment with trimethoprim-sulfamethoxazole.

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