By Caroline Kee

A parasitic infection that causes miserable bouts of watery, “explosive” diarrhea is surging across the United States. Several states are seeing cyclosporiasis rates that are unusually high for this time of year. Meanwhile, health authorities are scrambling to identify the source driving the outbreaks.

As of July 14, nearly 7,000 cases of cyclosporiasis have been reported by at least 34 states, according to the U.S. Centers for Disease Control and Prevention.

The CDC believes 400 of these cases in four states — Michigan, Ohio, West Virginia and Kentucky — are connected as part of a large, multistate outbreak, it said in a health alert on Tuesday.

The agency is also investigating several large clusters in other states, as well as potential sources.

“Cases are simply exploding across the country,” said ER physician Dr. John Torres. At least 141 people have been hospitalized so far.

Cyclosporasis rates normally increase in the U.S. during the warmer months, according to the the CDC. But the recent surge has sparked some concern.

The infection is caused by the Cyclospora cayetanensis parasite, which spreads through food and water contaminated with feces from an infected person, also known as the fecal-oral route. Person-to-person spread is highly unlikely, per the CDC.

In the U.S., cyclosporiasis outbreaks are commonly linked to fresh produce. When ingested, cyclospora infects the small intestine and leads to watery, explosive diarrhea.

Cyclosporiasis is usually not life-threatening, per the CDC. However, it is extremely unpleasant, and the episodes of severe diarrhea can last for weeks — which can put a real damper on vacation plans.

Where Are Cyclosporiasis Cases Rising?

Nationally, cyclospora infections have been ramping up since spring.

The CDC has received reports of 1,645 laboratory-confirmed cases of cyclosporiasis in 34 states since May 1, and is investigating over 5,100 probable cases.

“This is substantially higher than the 249 cases reported nationally by this same time last year,” the agency said.

The true number of people infected with cyclospora in the U.S. is likely higher than the numbers being reported because many people who get sick with diarrhea do not seek medical care or get tested for cyclospora.

The CDC’s national tally currently lags behind state health department data because the agency has to confirm all reported cases.

Some 35 states’ health departments responded to requests about recent cyclosporiasis spikes.

Here’s which states are reporting the most cases:

Michigan

Since late June, Michigan has seen a “sudden and large” increase in cases of the diarrhea-causing parasite.

As of July 15, Michigan has reported 3,762 cases of cyclosporiasis and 44 hospitalizations since the end of June, according to the Michigan Department of Health and Human Services.

That number is over 65 times higher than the annual average for the state, which records about 40-50 cases a year, a spokesperson for MDHHS said.

Dr. Natasha Bagdasarian, chief medical executive for the state of Michigan, said that the recent, sharp increase in cases is “highly unusual.”

Ohio

As of July 10, the Ohio Department of Health has reported at least 364 cyclosporiasis cases in 2026 — of those, at least 171 occurred since late June, a spokesperson for the Ohio Department of Health said.

“When we started seeing cases of persistent diarrhea showing up, we knew there’s something going on,” saod Dr. Brian Kaminski, vice president of medical affairs at ProMedica Health System, which sees patients in Michigan and Ohio.

New York

New York state has recorded approximately 394 cyclosporiasis cases since May 1, a spokesperson for the state health department said in a July 9 statement. Typically, the state records 500-700 cases a year.

“New York’s current case counts do not represent a major deviation from the norm this time of year,” the spokesperson said.

North Carolina

As of July 13, North Carolina has reported 240 cyclospora infections since May, according to a statement from the North Carolina Department of Health.

Illinois

The Illinois Department of Health said that the state has seen 216 cases as of July 14, a “higher than average” number, with no single potential cause identified.

Indiana

At least 206 cases have been reported in Indiana since May 1, a state spokesperson said.

Colorado

Colorado has reported 150 cases of cyclosporiasis as of July 14, said a public health spokesperson for the state.

West Virginia

West Virginia has reported 69 cyclosporiasis cases and at least eight hospitalizations as of July 13, according to a release from the West Virginia Department of Health, which is investigating an outbreak in the state.

Kentucky

Kentucky has reported some 100 cyclosporiasis cases this year — 55 cases have been confirmed, and at least seven people have been hospitalized, a spokesperson for the Kentucky Department for Public Health confirmed.

Kentucky normally sees about 35 cyclosporiasis cases per year.

Texas

Texas has reported 48 cases between May 1 and July 6, resulting in five hospitalizations and no deaths. No common source has yet been identified, per a statement from the Texas Department of Health.

Is There a Cyclosporiasis Outbreak in the U.S.?

Yes, the CDC and U.S. Food and Drug Administration are currently investigating several outbreaks of cyclosporiasis.

This includes a large, multistate outbreak occurring in Michigan, Ohio, Kentucky and West Virginia. Over 400 people have been infected in connection with the outbreak, which began at the end of June, the CDC said. The source is unknown.

It’s unclear if clusters and outbreaks in other states are also connected. Health officials are scrambling to track cases and interview those infected.

“Cyclospora investigations are particularly challenging and take a significant amount of time and effort,” Gwen Biggerstaff, deputy director of the CDC’s Division of foodborne diseases, told reporters in a briefing on July 14.

It’s not out of the norm to see cyclospora infections increase in the summer. In the U.S., cyclosporiasis season usually lasts from May to August, per the CDC.

However, the number of cyclosporiasis cases being reported is “unusually high” for this time of year, Biggerstaff said.

The national tally shows over 6,700 confirmed or probable cases have been reported in the U.S. in 2026 so far. Dianna Blau, acting chief of the CDC’s Parasitic Disease Branch, said that the U.S. reported 2,700 cyclosporiasis cases in all of 2025.

Health officials are racing to identify the source or sources of the outbreaks. So far, no specific food item has been identified, the CDC said.

On July 13, Michigan health officials announced that early results point to “lettuce or salad greens” as a potential source of the state’s outbreak, but that it could not rule out other foods.

In the past, cyclosporiasis outbreaks have been linked to salad greens, raspberries, basil, cilantro, green onions and snow peas.

Cyclosporiasis Symptoms

The most common symptom of cyclosporiasis is sudden, watery diarrhea. According to the CDC, these bowel movements are often frequent and “explosive.”

In addition to diarrhea, people may experience severe stomach cramps, bloating, vomiting, nausea, loss of appetite, and fatigue, per the Cleveland Clinic.

These can last for several days to several weeks or longer. The bouts of diarrhea may occur in cycles and “relapse” after you seem to feel better, the CDC says.

It can take up to 14 days after ingesting food or water contaminated with cyclospora for symptoms to start.

Compared to norovirus, another common illness that causes GI upset, cyclosporiasis typically takes longer to show symptoms and is more likely to cause diarrhea and cramping than vomiting, Bagdasarian said.

Most healthy people will recover from cyclosporiasis on their own, per the CDC, but the infection can be treated with a combination antibiotic. People with weak immune systems are at higher risk for recurring symptoms and may require more extensive treatment.

If you develop signs of cyclosporiasis or sudden and severe gastrointestinal illness, contact your health care provider.

How to Prevent Cyclosporiasis

The only way to prevent cyclosporiasis is to avoid consuming food or water that may be contaminated with feces.

Food safety experts said that at this stage, there is no reason for Americans to stop eating fresh produce due to the rise in cyclosporiasis.

“Almost all servings of fresh fruits and vegetables that you can buy on the market today are not linked to this outbreak,” said Donald Schaffner, Ph.D., a professor of food microbiology in the Department of Food Science at Rutgers University.

However, people can take extra steps in the kitchen.

Cooking food to 158 degrees Fahrenheit is the only way to destroy cyclospora. Freezing can inactivate the parasite, but it’s not a guarantee of safety.

Washing fresh produce can help lower the risk of cyclospora and other foodborne pathogens. “It’s not going to completely protect you, but it’s certainly going to minimize the amount of parasites that might be in there,” said Torres.

Here are a few more tips to prevent cyclospora from state health departments:

- Wash your hands with soap and water before and after handling raw produce.

- Thoroughly wash all fresh produce under clean, running water. Do not use soap.

- Scrub fruits and vegetables with a produce brush.

- Remove the outer layers, leaves and peel of produce when possible (such as with lettuce heads).

- Separate fresh basil and cilantro leaves and run them under running water before eating.

- Cut away any damaged areas on fresh produce before eating.

Michigan health officials have also shared “lettuce-specific safety measures” for people living in affected counties in the state.