Michigan is in the midst of the largest diarrheal disease outbreak in state history, and health officials are still unable to pinpoint the exact source of the disease. As of this week, more than 1,200 people in the state have been infected with the disease, and dozens have been hospitalized — and the outbreak does not remain within state borders. Here’s what’s already known, why it’s hard to track, and what health officials recommend in the meantime.
Key takeaways
- Michigan has confirmed 1,251 cases of Cyclospora as of July 9 — its largest outbreak ever — with 36 hospitalizations reported as of July 8.
- Ohio has 177 confirmed cases as of July 2, and investigations are open in 28 other states.
- Investigators have not been able to trace the source yet, since Cyclospora is difficult to test for and the incubation period can be one to two weeks.
- Officials currently recommend purchasing whole heads of lettuce instead of pre-washed packaged salad and cooking leafy greens when possible.
- Cyclosporiasis is treated with antibiotics — see a doctor if diarrhea persists for a long time rather than waiting.
The numbers behind the outbreak
As of July 9, the Michigan Department of Health and Human Services had confirmed 1,251 cases of cyclosporiosis statewide since the outbreak began on June 22 — up from 992 cases just a day earlier, showing how quickly the number continues to rise. As of July 8, 36 hospitalizations have been linked to the disease. In a typical year, Michigan sees approximately 50 cases total, making this the largest outbreak of its kind in the state’s history. The ages of people diagnosed range from 8 to 84 years, with an average age of 41 years, and no deaths have been reported.
The outbreak is not limited to Michigan. Neighboring Ohio has confirmed cases of its own — 177 reported as of July 2 — and similar illness is currently being investigated in 28 other states.
What causes this?
The culprit is Cyclospora, a microscopic, single-celled parasite that lives in feces and typically makes its way into food when crops are irrigated with contaminated water. It thrives in warm weather, which is part of the reason why cases tend to rise during the summer months. Previous outbreaks have been traced to sources such as imported berries, basil, snow peas and packaged salad mixes – but to date, no specific farmer, supplier or production type has been confirmed as the source of this particular outbreak.
Why is this outbreak particularly difficult to track?
There are some factors that make this investigation unusually difficult. Cyclospora is notoriously difficult to culture in the laboratory, and some standard tests do not detect it reliably. What’s more, the incubation period can last from one to two weeks, so by the time someone gets sick, the food causing the illness is often long gone — and a single bag of salad can be sourced from several different farms, which only makes it more difficult to pinpoint the exact origin. Health officials are now using genetic fingerprinting on samples to check whether cases share a common source.
What health officials recommend now
Because the source has not yet been identified, guidance has become more cautious. Officials currently advise people to buy whole heads of lettuce rather than pre-packaged salad, discard the outer two or three leaves, wash remaining leaves well under running water – and cook leafy greens when possible, as this is considered the safest option. The same goes for coriander and basil: separate the leaves, wash them well, and cook them when you can. For green onions, trim the root end, remove the outer layer, and wash well. As a general rule, cooking food to a temperature of 158 degrees Fahrenheit or higher kills the parasite, and all fresh produce should be washed under running water even if you plan to peel it. Cut products should also be refrigerated immediately.
Symptoms to watch out for
The characteristic symptom is watery diarrhea with frequent and sometimes explosive bowel movements, often accompanied by cramping, bloating, and fatigue. If left untreated, symptoms can last anywhere from a few days to more than a month, and can relapse. The common stomach bug tends to pass quickly; This usually doesn’t do that. If diarrhea persists for a long time, that’s the point of seeing a doctor instead of waiting.
The good news: It’s treatable
Although case numbers appear alarming, cyclosporiasis is treated with antibiotics, along with rest and staying hydrated. Health officials aren’t telling people to panic — the message is to be careful with products, pay attention to symptoms, and seek medical care right away if diarrhea persists rather than assuming it will pass like a typical stomach bug.
Frequently asked questions
Do I need to stop buying salad and berries completely?
Not quite, but current guidelines lean more cautious than usual: Officials recommend buying whole heads of lettuce rather than pre-washed packaged salad, discarding the outer leaves, washing them well, and cooking leafy greens when possible, because rinsing alone may not remove this parasite.
Why can’t investigators find the source of this outbreak?
Cyclospora is notoriously difficult to culture in the laboratory and some tests fail to do just that. Combined with a one- to two-week incubation period and products often sourced from multiple farms, tracking the exact origin has proven particularly difficult this time around.
Is this outbreak spreading beyond Michigan?
Yes. Neighboring Ohio has 177 confirmed cases as of July 2, and health investigations are currently open in 28 other states.
Is this disease treatable?
Yes — there is effective antibiotic treatment once the disease is diagnosed. The key is to see a doctor if diarrhea lasts too long rather than assuming it will pass like a stomach bug.
Quick start checklist
- ☐ Skip pre-washed bagged salad for now
- ☐ Buy whole heads of lettuce and discard the outer leaves
- ☐ Cook vegetables when possible, as rinsing alone may not be enough
- ☐ Wash berries, basil and other heavy produce well
- ☐ Refrigerate cut products immediately
- ☐ See a doctor if diarrhea lasts a long time — it can be treated with antibiotics
sources:
Michigan Department of Health and Human Services — Official outbreak page with daily updated case counts and safety recommendations
https://www.michigan.gov/mdhhs/keep-mi-healthy/infectious-diseases/infectious-disease-outbreaks
Click on Detroit — “Cyclosporiasis Outbreak: Michigan Cases Rise to More than 1,200” (July 9, 2026)
https://www.clickondetroit.com/news/local/2026/07/09/cyclosporiasis-outbreak-cases-in-michigan-rise-to-over-1200/
Disclaimer: This article is for general informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Case numbers reflect the most recent numbers reported as of the date of publication and may have changed since then. If you have persistent diarrhea or other worrisome symptoms, contact your health care provider immediately. For the latest official guidance and case numbers, consult the Michigan Department of Health and Human Services or the CDC.
