The largest outbreak in the nation of cyclosporiasis, the parasite known for causing “explosive diarrhea,” has expanded to four more states, federal health officials said Friday.
Cases of the intestinal infection have been rising nationwide since June, and last week, officials announced that an outbreak in five states had been linked to shredded lettuce sold at Taco Bell and supplied by Taylor Fresh Foods. (The fast-food chain pulled the affected lettuce from its menu, and the supplier issued a recall on all of its iceberg lettuce sourced from central Mexico.)
In Friday’s announcement, the Centers for Disease Control and Prevention said the outbreak now includes nine states: Illinois, Kansas, Oklahoma, Pennsylvania, Indiana, Kentucky, Ohio, West Virginia and Michigan. (The last five were previously linked.) The CDC has confirmed about 2,000 cyclosporiasis cases in these states.
In all of the U.S., there are almost 12,000 confirmed and probable cases across 41 states, per the CDC’s latest data. At least 308 people have been hospitalized. No deaths have been reported. On average, the entire U.S. sees about 3,000 cyclosporiasis cases a year.
Cases are also rising outside of the nine states in the outbreak. Since May, North Carolina has had over 500 cases, and New York over 600. Health officials are still investigating what may be driving these cases, as well as other possible sources of the large outbreak and if tainted lettuce went to other states.
Here’s what to know about where the parasite is surging in the U.S. and how to stay safe during peak fresh produce season.
What Is the ‘Diarrhea Parasite’ Going Around?
Cyclosporiasis is caused by Cyclospora cayetanensis, a microscopic parasite carried in human feces. People become infected by consuming food or water contaminated with particles of feces from an infected person, Kali Kniel, Ph.D., professor of microbial food safety at the University of Delaware, tells TODAY.com.
When ingested, cyclospora infects the small intestine and causes severe gastrointestinal upset. The main symptom of cyclosporiasis is watery, “explosive” diarrhea, which may persist for weeks, per the CDC.
Cyclosporiasis is usually not life-threatening, and most healthy people recover on their own, Kniel says. However, treatment with a combination antibiotic is highly effective.
After the parasite is shed in stool, it takes one to two weeks living outside the body to mature and become infectious, says Kniel, which makes person-to-person spread highly unlikely.
Cyclospora can get into produce if it’s grown in soil or washed with water contaminated with feces; fresh fruits and vegetables are common culprits, says Kniel.
Where Are Cyclosporiasis Cases Surging?
The CDC’s latest data show about 11,500 confirmed and suspected cases of cyclosporiasis reported in 41 states since May 1, which is the start of cyclosporiasis season in the U.S. Of these, the CDC has confirmed 4,173 cases and is investigating another 7,400 cases, the agency said.
The majority of the cases in the U.S. are in the Midwest, which is experiencing a large, multistate outbreak that began in late June. The U.S. Food and Drug Administration is also investigating five other cyclosporiasis outbreaks in the U.S., though it has not specified where they are.
Michigan is being hit the hardest. As of July 24, the state has reported 8,176 cyclosporiasis cases and 160 hospitalizations, per the Michigan Department of Health and Human Services.
Ohio has reported over 2,500 cases. Indiana and Illinois are each nearing 600 cases, and cyclosporiasis case counts have also surpassed 200 in Missouri, New York and North Carolina, based on information from state health departments provided to NBC News.
Beyond the nine-state outbreak linked to shredded lettuce, it’s unclear which clusters of cases in the U.S. may be connected, and investigations are ongoing, the CDC said.
“There may be multiple unrelated outbreaks going on at the same time,” Donald Schaffner, Ph.D., professor of food microbiology in the Department of Food Science at Rutgers University, tells TODAY.com.
The true number of cyclospora infections in the U.S. is likely higher than the numbers currently being reported. That’s because many people who get sick with diarrhea do not go to the doctor or get tested for cyclospora, per the CDC.
“We anticipate continuing to see cases increase, possibly through the end of August,” Gwen Biggerstaff, deputy director of the CDC’s Division of Foodborne, Waterborne and Environmental Diseases, said.
What Food Is Driving the Rise in Cyclospora Cases?
So far, the FDA and CDC have identified one possible source of cyclospora infections in the outbreak affecting nine states: shredded lettuce served at Taco Bell locations in these states.
Taco Bell has removed all affected lettuce from its supply chain. The supplier of the lettuce, Taylor Fresh Foods, recalled all of its iceberg lettuce products sourced from central Mexico from the U.S. market.
However, it’s possible that another source is also driving cases in the nine-state outbreak and elsewhere in the U.S. Officials in North Carolina said Tuesday that fresh parsley and cilantro may be behind the increase in cases there. Investigations are ongoing.
Schaffner and Kniel both suspect there’s more than one food or water source fueling the outbreaks nationwide.
Tracking Cyclospora Outbreaks
Cyclospora is a particularly challenging parasite to track, food safety experts tell TODAY.com.
Symptoms may not appear for up to 14 days, a longer incubation period than many other foodborne illnesses. Then, confirming a diagnosis through testing and being interviewed by an epidemiologist to investigate can take weeks or longer, says Schaffner. By that point, the person isn’t likely to remember what they ate that could’ve caused their symptoms.
As a result, only a small portion of cases every year get traced back to a particular food item.
It’s also worth noting that, in July 2025, the CDC’s foodborne surveillance network made testing for cyclospora optional, which could be impacting the response, Schaffner says. Federal health authorities have denied that changes to surveillance are affecting the investigation.
Foods to Avoid Due to the Cyclosporiasis Outbreak
The only way to prevent cyclosporiasis is to avoid food and water that may be contaminated with feces. So far, one recall has been issued due to the outbreak.
Taylor Fresh Foods is removing all iceberg lettuce products sourced from central Mexico from the U.S. market. While 33 out of the 35 affected products were sent to food service locations, two items were provided to Walmart and sold under the brand Marketside:
Iceberg Salad: 12 oz., 24 oz.; best if used by July 18–Aug. 3, 2026Shredded Lettuce: 8 oz., 16 oz.; best if used by July 18–Aug. 3, 2026
The recalled products were distributed to 27 states: Alabama, Arkansas, Connecticut, Florida, Georgia, Iowa, Illinois, Indiana, Kansas, Kentucky, Louisiana, Massachusetts, Maryland, Michigan, Missouri, Mississippi, North Carolina, New Hampshire, New Jersey, Ohio, Oklahoma, Pennsylvania, South Carolina, Tennessee, Texas, Virginia and Wisconsin.
The FDA is urging consumers not to eat any of the recalled lettuce, including at Taco Bell or other restaurants. It encourages consumers to ask about the source of iceberg lettuce before ordering it at a restaurant.
Health officials in North Carolina recently said fresh parsley and cilantro may be driving the cases there.
Still, experts are urging people not to panic.
“Almost all servings of fresh fruits and vegetables that you can buy on the market today are not linked to this outbreak, and are not any more likely to cause illness because of the outbreak,” says Schaffner.
“We know that fresh (produce is) part of a healthy diet, and I certainly don’t want to discourage that,” adds Schaffner, who still plans to enjoy his favorite fruits and vegetables this summer.
If you want to avoid certain foods out of an abundance of caution, past cyclosporiasis outbreaks in the U.S. have been linked to the following foods:
Salad greensCilantroBasilRaspberriesGreen onionsSnow peasHow to Prevent Cyclospora
Cooking food to least 158 degrees Fahrenheit is the best way to protect yourself, as heat destroys the parasite. Freezing can also inactivate cyclospora, but it’s not a guarantee.
Washing produce thoroughly can reduce the risk of foodborne illness, but it won’t eliminate cyclospora entirely.
Health authorities have offered a few more tips to prevent cyclospora infection:
Wash your hands well with soap and hot water before and after handling raw produce.Scrub all fresh fruits and vegetables with a produce brush under clean, running water. Do not use soap.Remove the outer layer of leaves or the peel, if possible. Run the inner leaves under running water.Cut or peel off damaged areas of produce before eating.
People with weakened immune systems may need to take extra precautions and should consult their doctor about how to avoid foodborne illness, says Kniel.
“We are seeing hospitalizations, so if you do get sick, good hydration is critical, and so is getting clinical care because this can be treated,” Kniel adds.
If you develop symptoms of cyclosporiasis, contact your doctor.