Explosive diarrhea parasite cases rise by thousands, now in 45 states

Mary Walrath-Holdridge, USA TODAYWed, July 29, 2026 at 2:30 PM UTC

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Cases of cyclosporiasis, a stomach-churning parasitic infection known for causing explosive diarrhea, have now reached 45 states as infections climb well into the thousands.

There have been 6,707 laboratory-confirmed cases of the illness since May 1, the Centers for Disease Control and Prevention said in its weekly update on July 28, a more than 2,500 increase since its last report on July 21. Cases have also now been recorded in 45 states, up from 41 last week. More than 11,500 additional cases, primarily in Michigan and Ohio, have not yet been confirmed by laboratories, the CDC said.

There have been 423 hospitalizations and no deaths, per the agency.

Federal health authorities are still investigating the sources of what they believe to be multiple separate outbreaks, the largest of which is centered in Michigan. The state reported more than 10,000 cases of cyclosporiasis on July 29 – numbers which differ from the CDC because they have not yet been officially confirmed and reported back to the federal agency for counting.

This largest outbreak has been linked to iceberg lettuce grown by produce giant Taylor Farms in central Mexico, prompting the company to initiate a recall on July 17.

"Cyclosporiasis cases may not be limited to these states with known cases," according to the CDC update. "The true number of people sick with cyclosporiasis was likely higher than the number reported. This is because some people recover without medical care and are not tested for Cyclospora."

See map of states with cyclosporiasis cases

Only Hawaii, Maine, Montana, New Mexico and South Carolina have been spared thus far from the outbreaks. Michigan and Ohio remain the two states most impacted, and Washington, DC, has also reported a handful of cases.

The CDC only reports lab-confirmed cases that occurred on or after May 1 in people who did not travel internationally within 14 days of illness onset. Its numbers often lag behind those cited by state health officials because of tracking, verification and reporting processes. There's typically a six-week reporting lag between an illness and the case being reported to the CDC.

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What is cyclosporiasis? What are the symptoms?

Cyclosporiasis is a parasitic infection that causes unpleasant gastrointestinal symptoms often associated with food poisoning, such as diarrhea, nausea and vomiting. It is caused by the parasite Cyclospora cayetanensis, also known simply as cyclospora, and is usually contracted through contaminated food or water.

While unpleasant, it is not generally known to cause death, and many cases go unreported, as people recover at home without visiting a doctor. It can cause more serious complications in people with compromised immune systems or other underlying health issues.

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The most common symptom is watery, frequent and sometimes "explosive" diarrhea, according to the CDC and Cleveland Clinic, though other troubles can include:

Vomiting.

Loss of appetite.

Bloating, including burping and gas, or stomach cramps.

Extreme tiredness (fatigue).

Fever.

Nausea.

Largest outbreak linked to lettuce hits 9 states as Michigan reports 10,000 cases

The Michigan-centered outbreak linked by the Food and Drug Administration to recalled iceberg lettuce from Taylor Farms has been identified as the largest nationwide, with the state reporting 10,077 cases as of July 29.

Illnesses from the lettuce outbreak have been confirmed in nine states, including Illinois, Indiana, Kansas, Kentucky, Michigan, Ohio, Oklahoma, Pennsylvania and West Virginia, according to the CDC.

These states were identified after health officials tested sick people and traced the "DNA," so to speak, of the infections to determine if they were related. Those that are related are considered part of the same outbreak, likely stemming from the same source. Thus far, these nine states are the only ones the CDC has been able to confirm as related to each other and trace back to the lettuce.

The source of a cyclosporiasis outbreak is more difficult to track than foodborne illnesses because of a long incubation period, difficulty obtaining samples and the inability to use the same genetic tracking tools available for pathogens like E. coli and listeria, as previously reported by USA TODAY.

Health authorities tracking several potential outbreaks

Several other, separate case clusters have been identified by the CDC and FDA, with no common cause yet named. And while Health and Human Services Secretary Robert F. Kennedy Jr.said in a July 21 news briefing that the outbreak was "under control," critics have pointed toward cuts to relevant health agencies, with some saying that scaled-back surveillance and limited staffing enabled not only the cyclospora spread, but other recent outbreaks like screwworm.

Last year, the CDC scaled back a decades-long federal-state partnership that monitors foodborne illnesses, including those caused by cyclospora.

Mexican health authorities, meanwhile, have also said there has not yet been ample evidence to support the FDA's assertion that the outbreak originated over the border, as reported by USA TODAY.]

(This story has been to add new information.)

Contributing: Melina Khan, Mike Snider, Sara Moniuszko, USA TODAY; Reuters

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