Michigan health officials reveal potential source for cyclosporiasis outbreak
Jul 13, 2026
With cases of a parasitic infection that causes “explosive diarrhea” climbing into the thousands in Michigan, state health officials believe they have the beginnings of a potential source for the outbreak.
In a new update Monday, the Michigan Department of Health and Human Services reported t
hat while its investigation into the more than 2,600 cases identified so far continues, “current results point to lettuce or salad greens” as a potential source.
The finding only applies to Michigan, and health officials noted that “other food items cannot be completely ruled out” and “no specific type of produce, grower or supplier has been identified as the source.”
“Although we do not have a definite product identified as the source of the outbreak, we want to let Michiganders know what we have learned so far so they can take steps to protect their families,” Dr. Natasha Bagdasarian, chief medical executive for MDHSS, said in a statement. “Early information has shown lettuce as a common product that regularly comes up during the investigation. We will continue to provide updates as we learn more.”
Known for causing watery diarrhea, nausea and stomach pains, cyclosporiasis is an infection caused by a parasite often linked to contaminated food and water.
Michigan health officials said while they typically only record 40-50 cases annually, they have already seen 2,640 in a matter of weeks.
“MDHHS continues to work closely with local health departments to conduct in-depth interviews of individuals testing positive for cyclosporiasis, as well as with other state and federal partners to conduct traceback investigations. More than 1,000 interviews have than have been completed to date,” the department said in a release. “Given the extent of the outbreak, the incubation period of up to two weeks for symptoms to develop after exposure and complex food distribution networks across the state and country, it will take some time for agencies to complete their investigation.”
While the infections can be contracted from swimming in contaminated waters, such transmission is uncommon and Michigan health officials said it is “not a recognized risk factor” and “there is currently no evidence linking recreational water activities to this outbreak.”
Instead, they have said foodborne exposure remains the primary focus for the latest outbreak, which has sparked cases nationwide.
The Centers for Disease Control and Prevention reported Friday that 31 states have reported cases of cyclosporiasis and 86 people have been hospitalized.
It remains unclear whether there is currently a single or multistate outbreak linking all cases.
What can you do to prevent infection?
While lettuces are being investigated as a potential source, and have been the source for previous cyclosporiasis outbreaks, officials urged anyone eating or preparing lettuce or salad greens in areas where cases have been reported to take added precautions.
That includes:
Purchase whole heads: Buy whole heads of lettuce rather than pre-washed, bagged lettuce or pre-mixed salad kits.
Discard outer layers: Before preparation, throw away the outer two to three layers of leaves.
Wash inner leaves: Thoroughly wash the remaining inner leaves under clean running water.
Prioritize cooking: For any greens that can be cooked, cooking to a temperature of at least 158 F (70 C) is the safest option, as the parasite is resistant to routine chemical disinfection and washing alone cannot guarantee its removal.
Other recommendations include:
Cook produce when possible: Heating food to 158 F (70 C) or higher kills cyclospora.
Peel produce: Peeling is highly effective for food items with removable skin as the parasite sits on the outer surface.
Wash all fresh produce: Wash under clean running water, even if you plan to peel it. “Pre-washed” does not guarantee safety and rewashing bagged lettuce is unlikely to remove cyclospora. While washing alone may not fully eliminate cyclospora, it enhances protection when combined with cooking or peeling.
Produce items linked to previous outbreaks
Food items that have been linked to previous cyclospora outbreaks in the U.S. and Canada include:
Bagged salad mixes and kits
Fresh cilantro (coriander leaves)
Fresh basil
Raspberries
Snow peas
Green onions (scallions)
Symptoms of cyclosporiasis
While the most common and notable symptom of the infection is known as “explosive diarrhea,” there are numerous other signs of infection.
“[The diarrhea] can be really frequent, pretty severe. People talk about explosive diarrhea,” said Dr. Kiran Joshi with the Cook County Department of Public Health. “You can get all kinds of other abdominal symptoms as well, including loss of appetite, nausea, vomiting, sometimes a low grade fever. Now, those symptoms can certainly cause quite a bit of distress. The good news is that this is typically not a life-threatening illness, though if untreated, it can last for a month or longer, so it’s really important.”
Experts say diarrhea itself isn’t a distinctive symptom, but knowing the outbreak is growing could lead more practitioners to testing for cyclosporiasis.
“There are a lot of different causes of diarrhea, and cyclosporiasis is not one of the higher causes of infectious diarrhea. But when cases do surge in the way that they are, it’s important to pay attention to it,” Mayer said.
One of the larger indications of cyclosporiasis is likely the timing of infection and symptoms.
While many other foodborne illnesses will show symptoms within hours, cyclosporiasis can take days or even up to two weeks to appear. The most common time frame is around one week, according to the Centers for Disease Control and Prevention.
“The first thing is explosive diarrhea, bloating, cramping, loss of appetite,” Dr. Sharon Welbel, chair of infectious diseases for Cook County Health, said. “Some people have a low-grade fever but that’s pretty uncommon.”
The infections can also last much longer than other foodborne illnesses.
“The symptoms are a bit less, but they go on longer. Noroviruses kind of hits you hard and then it’s done. This kind of just drags on for a longer period of time,” Dr. Irfan Hafiz, an infectious disease physician at Northwestern Medicine, told NBC Chicago.
The CDC notes that the illness can last anywhere from a few days to over a month and, in some cases, may even seem to go away but then return one or more times.
Here’s a look at how it compares to other illnesses.
What to do if you become ill
People experiencing frequent, watery diarrhea are being urged to contact their healthcare provider and “specifically request testing for cyclospora as routine stool tests may miss the parasite,” MDHSS stated.
Treatment for confirmed infections will include antibiotics, but those who contract it should also be prepared to rest and drink fluids to maintain hydration.
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