A parasitic infection that causes miserable bouts of “explosive” diarrhea is surging across the United States at rates that appear to be higher than this time last year. Meanwhile, public health authorities are racing to identify the source or sources driving the surge.
As of July 10, over 3,000 cases of cyclosporiasis have been reported, according to NBC News’ latest tally based on information from state health departments. Meanwhile, the U.S. Centers of Disease Control and Prevention confirmed 843 cases from 31 states had been reported to them as of July 9.
According to NBC News reporting, Michigan, New York, Ohio, Illinois and North Carolina are among the states hit hardest by the parasitic stomach bug. Rates usually increase during the warmer months in the United States, according to the CDC.
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. In the U.S., it’s commonly linked to fresh fruits and vegetables.
When ingested, cyclospora infects the small intestine and leads to watery, uncontrollable diarrhea and other gastrointestinal symptoms. Person-to-person spread is uncommon.
Cyclosporiasis is usually not life-threatening, per the CDC. However, it is extremely unpleasant, and the episodes of severe diarrhea can last for several weeks — which can put a real damper on vacation plans. Some patients experience relapsing symptoms, meaning they stop and then return.
There’s no evidence the illness clusters are related so far, the CDC said, but investigations are ongoing.
“When we started seeing cases of persistent diarrhea showing up, we knew there’s something going on,” Dr. Brian Kaminski, vice president of medical affairs at ProMedica Health System, which sees patients living Michigan and Ohio, told NBC News. “I would say that trend continues.”
Dr. Natasha Bagdasarian, chief medical executive for the state of Michigan, told NBC News that the recent, sharp increase in cases is “highly unusual.”
Where Are Cyclosporiasis Cases Rising?
Nationally, cyclospora infections have been ramping up since spring.
According to the latest surveillance data from the CDC, at least 843 cases of cyclosporiasis have been reported in 31 U.S. states since May 1. (This data does not include all the latest case counts reported by state health departments.)
Among those sickened, at least 86 have been hospitalized.
In a July 10 update, the CDC also said “it is aware of more than 1,500 cases that require further analysis to confirm the illness as domestically acquired cyclosporiasis.”
The true number of people infected with cyclospora in the U.S. is likely higher than the numbers being reported “because some people recover without medical care and are not tested for cyclospora,” the CDC said.
Thirty states’ health departments responded TODAY.com and NBC News about whether there have been recent cyclosporiasis spikes.
Michigan
In Michigan, health officials are seeing an unprecedented “sudden and large” increase in infections with the diarrhea-causing parasite, TODAY.com reported previously.
As of July 10, Michigan has reported 1,562 cases of cyclosporiasis since the end of June, according to the Michigan Department of Health and Human Services. That’s nearly 25 times higher than the annual average for the state, which records about 40-50 cases a year, a spokesperson for MDHHS told TODAY.com.
The majority of cases are in Southeast Michigan in the following counties: Monroe, Lenawee, Washtenaw, Wayne, Shiawassee, Jackson, Oakland and Livingston.
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.
The recent surge in cases in Michigan and bordering Ohio may be part of an “epidemic cluster,” Kaminski said.
New York
New York state has recorded approximately 394 cyclosporiasis cases since May 1, a spokesperson for the state health department told TODAY.com 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.
Illinois
The Illinois Department of Health told NBC News that the state has seen 141 cases this year, a “higher than average” number, with no single potential cause identified.
North Carolina
As of July 10, North Carolina has reported 205 cyclospora infections since May, according to a statement from the North Carolina Department of Health to NBC News.
Colorado
Colorado has reported 90 cases of cyclosporiasis so far, a public health spokesperson for the state told NBC News.
Indiana
Some 72 cases have been reported in Indiana since May 1, a state spokesperson told NBC news.
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.?
It’s not out of the norm to see cyclospora infections increase around this time of year. In the U.S., cyclosporiasis season usually lasts from May to August, per the CDC.
However, it appears there may already be more cases reported this year than last year. NBC News’ tally shows over 3,000 reported or confirmed cases nationally, compared to about 2,700 cases for all of last year, according to Dianna Blau, acting chief of the CDC’s Parasitic Disease Branch.
“So far this year, multiple states have reported an increase in cases in the last two weeks compared to the same period in 2025,” the CDC said in a July 10 update on its website.
However, the agency clarified that it “has no evidence of a single, multistate Cyclospora outbreak linking cases happening right now and being reported in the press,” a spokesperson told NBC News in an email.
The CDC and FDA are currently monitoring clusters of cases in multiple states. “We are not in a position at this time to characterize the current numbers as definitively unusual pending the completion of that investigation,” a U.S. Food and Drug Administration spokesperson told NBC News.
The massive increase in cyclosporiasis in Michigan and other states has prompted investigations into a potential common source. So far, no food, grower or supplier has been identified.
The current hypothesis is that contaminated fresh produce is driving the surge, Bagdasarian said. In the past, cyclosporiasis outbreaks have been linked to salad greens, raspberries, basil, cilantro, green onions and snow peas.
Health officials are urging people to seek treatment if they experience cyclosporiasis symptoms.
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 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 bouts of severe gastrointestinal illness, contact your health care provider.
How to Prevent Cyclosporiasis
The only way to prevent cyclosporiasis is to cook it to at least 158 degrees Fahrenheit, or to avoid food and water that may be contaminated with feces. Freezing may also kill the parasite, but it’s not a guarantee.
State health authorities offered a few more tips to prevent the spread of cyclospora:
- Wash hands with soap and water before and after handling raw produce.
- Thoroughly wash all fresh produce under running water before eating it. Do not use dish soap.
- Scrub fruits and vegetables with a produce brush.
- Remove the outer layer of produce when possible (such as with lettuce heads, green onions, etc.).
- Separate fresh basil and cilantro and run them under running water before eating.
- Cut away any damaged areas on fresh produce before eating.
- Refrigerate fruits and vegetables (cooked or fresh) within two hours of preparing it.
Food safety experts told NBC News there is no reason to stop eating fresh fruits and vegetables due to the recent rise in cases, as doing so is a crucial part of a healthy diet.
