Cyclospora, a microscopic parasite that causes an intestinal infection, is behind a fast-growing outbreak across at least 25 states this summer, with Michigan alone reporting nearly 1,200 confirmed cases by early July compared to a typical annual total of about 50. Ohio, Illinois, New York, and North Carolina are also seeing sharply elevated numbers.
Here’s what to know if you live in an affected area, what the seven main symptoms look like, and when to seek care.
What Cyclospora Is
Cyclospora cayetanensis is a single-celled parasite that infects the small intestine. It’s spread through food or water contaminated with human feces. Not person-to-person, and not the same organism as the bacterial or viral bugs that cause most cases of “stomach flu.”
Foodborne outbreaks in the US have historically been linked to specific types of fresh produce: raspberries, basil, snow peas, cilantro, mesclun lettuce, spinach, and various berries. In the current 2026 outbreak, investigators have not yet identified a common food source, though contaminated produce remains the working hypothesis.
Once ingested, the parasite takes about 7 to 10 days to cause symptoms, with a range of 2 to 14 days.
Where the Outbreak Is Right Now
The CDC confirmed 145 domestically acquired cases across 17 states between May 1 and June 16, 2026. Michigan then added a rapid surge, reaching 678 confirmed cases by July 6, mostly in the southeast region including Wayne County. Ohio has reported 177 cases (171 of those since June 20), Illinois 141 cases, North Carolina 110, New York 120 since May 1, and Texas 48.
Michigan’s chief medical executive described the case count as a “moving target” that’s likely to keep rising. Normally, the state records about 50 cases in an entire year, so current numbers are running roughly 13 times the annual average.
The CDC has not yet linked cases into a single multistate outbreak. Multiple clusters are under active investigation, all likely food-related.
The 7 Symptoms to Watch For
1. Watery Diarrhea
The hallmark symptom, often described as “explosive.” Frequent, watery, and urgent. Different from the semi-formed diarrhea of many stomach bugs. This is the symptom most likely to send someone to a doctor.
2. Abdominal Cramping and Pain
Often severe. Concentrated in the mid-abdomen, sometimes shifting with each bout of diarrhea. Can be strong enough to disrupt sleep.
3. Nausea
Common but not always dominant. Some patients have nausea without much vomiting, which sets cyclosporiasis apart from many viral causes of GI illness.
4. Loss of Appetite and Weight Loss
Because the illness can drag on for weeks without treatment, appetite loss and gradual weight loss are common. Some patients lose 5 to 10 pounds before they get a diagnosis.
5. Fatigue
Deep, hard-to-shake fatigue that doesn’t improve with rest. Often the symptom patients mention first when their story doesn’t fit a typical stomach bug.
6. Low-Grade Fever
Often mild, in the 99 to 100.5°F range. Not always present. Higher fevers or shaking chills should prompt evaluation for other causes.
7. Symptoms That Come and Go
Perhaps the most useful diagnostic clue. Cyclosporiasis often relapses. Patients feel better for a few days, sometimes even a week, then symptoms return. Untreated, this cycle can continue for weeks or months.
If watery diarrhea has lasted more than 5 to 7 days, or has cleared and returned once already, it’s worth asking specifically about cyclospora.
Why Testing Matters
Standard stool tests often miss cyclospora. To confirm the diagnosis, clinicians typically need to request either modified acid-fast staining or specific PCR testing. Neither is part of most routine diarrhea panels, so patients often need to ask for it directly, especially if they live in an affected state or have had persistent watery diarrhea for more than a week.
Treatment is trimethoprim-sulfamethoxazole (TMP-SMX, also sold as Bactrim or Septra). For patients with sulfa allergies, alternatives exist but are less well-studied.
Without treatment, cyclosporiasis can last several weeks. With treatment, most people improve within a few days.
When to See a Doctor
Reach out to a doctor if you’ve had watery diarrhea for more than 3 days without improvement, if symptoms cleared and came back, if you’re losing weight, if you feel severely fatigued out of proportion to the illness, or if you have signs of dehydration (dizziness, dry mouth, decreased urination).
For anyone in Michigan, Ohio, Illinois, or another state with significant reported cases, prolonged watery diarrhea should specifically prompt a conversation about cyclospora testing.
How to Lower Your Risk
Wash all fresh produce carefully before eating, especially berries, herbs, and leafy greens. The parasite isn’t always removed by rinsing alone, but a thorough wash reduces risk. Peel fruits when possible. During active outbreaks, some infectious disease specialists recommend cooking produce that would otherwise be eaten raw.
When traveling, avoid tap water in countries where cyclosporiasis is common. Use bottled water for drinking and brushing teeth. Skip raw produce that hasn’t been peeled by you.
Cyclospora isn’t spread person to person, so household isolation isn’t necessary. But if you’re symptomatic and preparing food for others, be diligent about handwashing.
Where ChatRx Fits
Cyclosporiasis needs specific testing and a specific antibiotic. It’s not one of the conditions we treat directly. Where ChatRx fits is in the earlier stages, when it’s not yet clear what’s causing the diarrhea. If you’re in Indiana, Illinois, or Michigan and dealing with symptoms that could be viral gastroenteritis, food poisoning, or something else, our doctors can review your case, prescribe anti-nausea medication when helpful, and steer you toward the right in-person care if the pattern suggests cyclospora or another condition requiring lab work.
Chat-based, $25 flat. The free symptom checker can also help you sort what to do next. No account required.
Quick Take
Cyclosporiasis cases are climbing sharply this summer, especially in Michigan, Ohio, Illinois, and neighboring states. Watery “explosive” diarrhea lasting more than a few days, especially in a cyclical pattern, is the classic pattern to watch for. Standard stool tests can miss the parasite, so patients often need to ask specifically for testing. Treatment with TMP-SMX is highly effective. If you or someone in your household has persistent watery diarrhea right now, don’t wait it out.
Frequently Asked Questions
Yes. There’s no lasting immunity after infection, so reinfection is possible, especially during an active outbreak season.
Yes. Cyclospora doesn’t survive cooking, so cooked produce carries essentially no risk. It’s raw produce, especially berries and leafy greens, where the risk lives.
Most people improve within a few days of starting treatment. If symptoms haven’t improved after several days on TMP-SMX, that’s worth a follow-up conversation with a doctor.
Disclaimer
This information is provided for educational purposes only and is not intended to replace professional medical advice, diagnosis, or treatment through ChatRx. If you have questions about a medical condition, talk with a qualified healthcare provider. Services like ChatRx can help connect you with licensed physicians.
