Across the United States, a summer stomach illness with an alarming description is drawing attention from health officials: frequent, watery and sometimes “explosive” diarrhea.
The illness is called cyclosporiasis. It is caused by the microscopic parasite Cyclospora cayetanensis, and federal health officials say they are tracking 145 domestically acquired cases across 17 states. Twenty people have been hospitalized, and no deaths have been reported, according to the Centers for Disease Control and Prevention’s July 1 update.
The word “outbreak” makes people think of a single contaminated product or one clear source. But the CDC is being more careful. It says there is currently no evidence of a single multistate Cyclospora outbreak connecting all reported cases. Instead, officials are tracking a surveillance count nationwide while investigating several clusters and potential food sources.
That distinction matters. This is not yet a simple “avoid this product” story. It is a summer food safety story with an unfinished map, an unidentified source, and a parasite that can turn an ordinary meal into weeks of illness.
What is happening now
The CDC says the 145 U.S.-acquired cases involve people who became sick between May 1 and June 16, 2026. These patients did not report international travel in the 14 days before becoming ill, suggesting they were exposed through food or water in the United States.
The agency says patients ranged in age from 5 to 86, with a median age of 42, and 61 percent were female. Of the 145 people with available information, 20 were hospitalized.
The states identified in the reporting, based on the CDC map, include New York, Pennsylvania, New Jersey, Connecticut, Alaska, Colorado, Florida, Georgia, Illinois, Louisiana, Massachusetts, North Carolina, Ohio, Tennessee, Texas, Virginia, and Wisconsin. New York has reported the highest number of cases, while Texas and Illinois are also among the states with higher case counts.
There is also a separate and rapidly growing Michigan situation. Michigan health officials said more than 170 cyclosporiasis cases had been reported as of June 30 across several counties, including Monroe, Lenawee, Washtenaw, Wayne, Livingston, Shiawassee and Jackson. Michigan officials said the state typically identifies around 50 cases per year.
Why does this illness feel different from a normal stomach bug?
Most people have had a stomach bug and know the basic pattern: sudden discomfort, a rough day or two, then recovery.
Cyclospora can behave differently.
The CDC says symptoms usually begin about one week after someone consumes contaminated food or water, although they can appear as soon as two days or as late as two weeks or more after exposure. The most common symptom is watery diarrhea, but people may also experience loss of appetite, weight loss, cramping, bloating, gas, nausea, and fatigue. Less common symptoms include vomiting, body aches, headache, low-grade fever, and other flu-like symptoms.
The timeline is what makes this parasite especially frustrating. Without treatment, symptoms can last from a few days to a month or longer. They may also seem to go away, then return.
That relapse pattern can make people think they are recovering, only to be pulled back into the illness again.
How Cyclospora spreads
Cyclospora spreads when people consume food or water contaminated with feces containing the parasite. In the United States, past cyclosporiasis outbreaks have been linked to different types of fresh produce.
This is why the current investigation is focused heavily on food. The CDC says local, state, and federal officials, including the FDA, are investigating several clusters, but no single source has been identified for all cases.
One key point should calm some public fear: Cyclospora is not usually spread directly from person to person. The CDC explains that after the parasite passes in a bowel movement, it needs at least one to two weeks in the environment before becoming infectious. That makes direct person-to-person spread unlikely.
In plain language, this is not like a typical stomach virus sweeping through a household overnight. The concern is primarily about contaminated food or water, especially during spring and summer, when cases usually rise. The CDC considers May 1 through August 31 the main cyclosporiasis season.
Why fresh produce is part of the concern
Fresh produce is central to the concern because many fruits, vegetables, and herbs are eaten raw. That means there is no cooking step to kill pathogens before the food reaches the plate.
The CDC says no one fully knows how Cyclospora gets into food and water. But the best prevention strategy is to avoid food or water that may be contaminated with feces and to follow safe handling practices for produce.
That creates a difficult reality for consumers. People cannot see Cyclospora on lettuce, berries, herbs, or vegetables. They cannot smell it. They cannot taste it. A salad can look fresh and still be part of a public health investigation.
That is why this story lands differently from a normal food recall. There is no single bag, brand, or restaurant chain for the public to avoid right now. The advice is broader: handle fresh foods carefully, pay attention to symptoms, and take persistent diarrhea seriously.
What should people do at home?
The CDC recommends washing hands with soap and water before and after handling raw fruits and vegetables. It also recommends washing fruits and vegetables thoroughly under running water before eating, cutting, or cooking, and scrubbing firm produce such as melons and cucumbers with a clean produce brush. Damaged or bruised areas should be cut away, and cut, peeled, or cooked fruits and vegetables should be refrigerated within two hours.
That guidance may sound basic, but it matters because summer eating often means more raw produce, more outdoor meals, more potlucks, more travel, and more meals prepared in a hurry.
Washing produce does not guarantee that all risks disappear. But careful handling can reduce exposure to many foodborne contaminants and gives households a practical step while officials continue searching for the source.
When to call a doctor
Anyone with ongoing watery diarrhea, especially if it is severe, recurring, or accompanied by dehydration symptoms, should contact a healthcare provider.
The CDC says cyclosporiasis is diagnosed through stool testing, but labs may need special testing for Cyclospora because routine stool testing may not detect it. Some patients may need to submit more than one stool sample on different days.
Treatment is available. The CDC says trimethoprim-sulfamethoxazole, sold under names including Bactrim, Septra, and Cotrim, is the treatment of choice for cyclosporiasis. People who are allergic to sulfa drugs should talk with their healthcare provider about options. Rest and fluids are also important for people dealing with diarrhea.
Most healthy people eventually recover without treatment, but the illness can be prolonged if untreated, and people in poor health or those who are immunocompromised may face a higher risk of severe or long illness.
Why the real number may be higher
The CDC warns that the true number of illnesses is likely higher than the number reported. Some people recover without medical care, while others may not be tested for Cyclospora.
That undercount is common in foodborne illness investigations. Many people treat diarrhea at home, assume it is a viral infection, blame something they ate, and never seek care through the public health system.
But those missing cases matter. They can make it harder for investigators to find patterns, connect meals, identify common ingredients, and trace a contaminated source through the supply chain.
That is why public health interviews matter. When diagnosed patients share what they ate and where they shopped or dined, investigators can look for overlaps that may not be obvious to any one person.
The bigger story: summer food systems are complicated
This parasite story is also a reminder of how complex the modern food system has become.
A single salad can contain ingredients grown in different places, processed in different facilities, packed under different labels, and distributed across multiple states. If a parasite contaminates one ingredient, it can take weeks for investigators to connect the dots.
That complexity helps explain why officials have not yet named one product. Foodborne illness investigations depend on timelines, patient interviews, laboratory testing, purchase records, distribution data, and traceback work.
The public often wants a simple answer immediately. Public health rarely gets one that fast.
A careful warning, not a panic headline
The phrase “explosive diarrhea” is attention-grabbing, but the public health message should be measured.
The CDC has reported 145 domestically acquired cases across 17 states, 20 hospitalizations, and no deaths as of its latest national update. It has not identified one single multistate outbreak linking all cases. It is investigating clusters and possible sources.
That means people should be alert, not alarmed.
The best response is practical: wash hands, wash produce, refrigerate cut foods quickly, contact a doctor for persistent symptoms, and cooperate with health departments if diagnosed.
The danger hiding in ordinary summer food
What makes cyclosporiasis unsettling is not just the symptom. It is the ordinariness of the possible exposure.
A salad. A bowl of fruit. A garnish. A quick lunch. A summer meal that looks clean and healthy.
That is the quiet challenge for investigators and consumers alike. The parasite does not announce itself. It travels through food systems invisibly, waits days before symptoms begin, and can leave people sick long after they expected a stomach bug to pass.
For now, the national map is still being filled in. The source is still under investigation. And the safest message is simple: treat fresh food carefully, treat persistent diarrhea seriously, and remember that in summer, even the healthiest-looking plate deserves attention.
