Cases of a Parasitic Infection That Can Cause Diarrhea for Weeks Are Rapidly Rising in the U.S. Here’s What to Know

The illness is caused by the microscopic parasite Cyclospora cayetanensis, which spreads via food or water contaminated with feces, usually on farms. Health officials are still investigating the source of the multistate outbreak

Sara Hashemi | Daily Correspondent

July 10, 2026 3:26 p.m.

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Cases of a parasitic infection that can cause “explosive” diarrhea have surged across the United States in recent weeks, according to health officials.

While the country typically logs a few hundred cases of the illness, called cyclosporiasis, per year, there have already been more than 1,500 cases reported in Michigan alone in 2026. Other states are also seeing more diagnoses than usual.

Here’s what you should know about cyclosporiasis.

What is cyclosporiasis?

The gastrointestinal illness is caused by a microscopic parasite called Cyclospora cayetanensis that spreads through feces-contaminated food or water. It generally peaks in the late spring and summer.

Although the infection usually isn’t life-threatening, its symptoms can be brutal: diarrhea, frequent explosive bowel movements, cramps, bloating and nausea. Some people also run a fever, but that’s less common, says Rebecca Schein, an infectious diseases expert at Michigan State University Health Care, to Brenda Goodman at CNN.

“It’s just more very watery diarrhea. More than three times a day and then feeling kind of bloated, full, uncomfortable,” Schein says. “Sort of like you just ate Thanksgiving dinner, but every day.”

One woman described her symptoms as a combination of illnesses. “It felt like I had Covid fatigue because my body felt so weak, but then it also felt like I had norovirus that wasn’t ending,” says Galenn Sekulich, who started feeling sick on June 21, to Sara Moniuszko at USA Today. She’s still struggling to eat foods beyond toast.

Symptoms can last between a few days and a few weeks and lead to rapid weight loss. Sekulich tells USA Today that she dropped ten pounds in five days.

Diagnosis requires a special test of stool samples—up to three specimens each taken at least 24 hours apart, according to Texas Health and Human Services. Most people with cyclosporiasis tend to recover with a days-long course of antibiotics.

Where are cases rising?

Michigan is getting the worst of it, though the state’s proactiveness in investigating and reporting cases may be “part of the reason why this looks like a Michigan problem,” says Natasha Bagdasarian, the state’s chief medical executive, to Mike Stobbe at the Associated Press.

There have also been about 500 cyclosporiasis cases identified in New York State, per the New York Times’ Alice Callahan. And Ohio has reported 177 cases as of July 2. There are at least nine clusters nationwide, according to CNN, affecting people in Texas, Illinois and Pennsylvania, among other states.

“There is clearly a linked outbreak happening right now,” Bagdasarian tells the AP.

The Centers for Disease Control and Prevention (CDC) notes that its national numbers are lagging behind reports at the state level.

What’s causing the current outbreak?

Health officials are still investigating the source—or sources—of the ongoing outbreak, according to the CDC. Past outbreaks across the globe have often been linked to contaminated fresh produce, primarily raspberries, basil, cilantro and salad mixes.

Because contamination usually occurs at the farm or irrigation level, traceback investigations are difficult, write epidemiologists Gage Moreno, of the Broad Institute of MIT and Harvard, and Caitlin Rivers, of the Johns Hopkins Bloomberg School of Public Health, in the newsletter FOI Clinical. Individuals who have recently been afflicted with cyclosporiasis got sick after eating food in the United States and did not report any travel in the 14 days before they became ill, per the CDC.

Janet Hamilton, executive director of the Council of State and Territorial Epidemiologists, tells Lena H. Sun at the Washington Post that with so many cases, “we know there has to be a source people are being exposed to—a contaminated food or product. It’s not spread person to person.”

The source is likely still out there given how quickly cases are rising, she adds.

How can I protect myself?

The best way to dodge the parasite is to avoid consuming anything that may have been contaminated. The Food and Drug Administration recommends washing your hands for 20 seconds with soap and warm water before and after handling raw fruits and vegetables. You should also wash produce thoroughly before peeling, eating or cooking it. Firm fruits and vegetables, like melons and cucumbers, should be scrubbed with a clean brush.

When you’re washing your produce, don’t use dishwashing soap, since it could also upset your stomach, says Janet Buffer, a food safety and nutrition expert at George Washington University’s Milken Institute School of Public Health, to Erika Edwards at NBC News. Instead, “agitate the surface vigorously.”

You should also cook produce whenever possible, since that’s the best way to kill any pathogens. However, don’t feel the need to avoid fresh fruits and vegetables entirely.

“We know that fresh produce is part of a healthy diet. We know that cyclospora cases peak between May and August, which is also prime fresh produce eating season,” says Donald Schaffner, a food microbiologist at Rutgers University, to NBC News. “I can tell you that I’m not going to change my consumption habits.”

Sara Hashemi | Read More

Sara Hashemi is a science writer and fact-checker currently based in New York City. Her work has appeared in Sierra, The Body, Maisonneuve magazine and more.