Cora NelsonA parasitic outbreak is spreading across the United States this summer, with federal health authorities confirming at least 145 people infected across 17 states as of mid-June 2026. The culprit is Cyclospora cayetanensis — a microscopic parasite that targets the small intestine and causes an illness known as cyclosporiasis, commonly described in clinical settings as producing "explosive" diarrhea. The Centers for Disease Control and Prevention (CDC) is actively investigating the source, and no recalls have been announced yet.
What Is Cyclospora and How Does It Spread?
Cyclospora cayetanensis is a single-celled parasite found in contaminated food or water. Unlike many foodborne pathogens, it cannot be spread directly from person to person. Infection occurs after consuming fresh produce irrigated with contaminated water.
Previous U.S. outbreaks have repeatedly been linked to imported fresh herbs and leafy greens — particularly cilantro, basil, and salad mixes with ties to Mexican growing regions. While federal investigators have not yet identified a single food source for the 2026 outbreak, the broad geographic spread across 17 states with no obvious regional clustering is consistent with contaminated produce distributed nationally through major commercial supply chains.
Critically, the parasite is not destroyed by standard produce washing. Cyclospora is only reliably killed by cooking — which means the produce most commonly implicated in outbreaks, eaten raw in salads and fresh herb garnishes, carries the highest risk.
How Serious Is the Current Outbreak?
Among the 145 confirmed cases reported to the CDC by June 16, 2026, 20 people required hospitalization — roughly 14% of those reported. Patients ranged in age from 5 to 86 years old, with a median age of 42, and 61% of cases were female. No deaths have been reported.
Illness onset dates ran from May 1 through June 6, with a median onset of May 13 — suggesting that for many current patients, exposure happened weeks ago. The parasite has an incubation period of 2 days to 2 weeks, meaning new diagnoses will continue to emerge in the coming weeks.
Separately, southeast Michigan is contending with a locally concentrated cluster: more than 170 cases of cyclosporiasis were reported in that region from June 22 onward, which investigators are treating as a potentially distinct exposure event.
Health authorities also caution that 145 confirmed cases is almost certainly a significant undercount. Cyclospora requires a specific laboratory stool test that is not part of routine analysis. Many infected people are never tested, never diagnosed, and never appear in CDC surveillance data — meaning the true case count is likely far higher.
Recognizing the Symptoms
The signature symptom is watery, sometimes explosive diarrhea that often comes and goes in waves. Many patients report feeling temporarily better, only to relapse. Additional symptoms include:
- Severe abdominal cramping and bloating
- Nausea and heartburn
- Profound fatigue
- Loss of appetite and unintended weight loss
- Excess intestinal gas
Symptoms typically begin about one week after exposure and, without treatment, can persist for weeks or even months in otherwise healthy adults. Fatigue in particular may linger well after the active gastrointestinal phase ends.
This article is for informational purposes only and does not constitute medical advice. If you suspect a foodborne parasitic infection, consult a licensed healthcare provider for diagnosis and treatment.
When Should You See a Doctor?
Cyclospora is not an illness to manage at home without medical attention. Clinical guidance recommends contacting a healthcare provider promptly if:
- You are experiencing multiple bouts of watery diarrhea per day
- Symptoms have lasted more than one week without clear improvement
- You show signs of dehydration: dry mouth, dark urine, dizziness, or reduced urination
- You have traveled recently to Central America, Mexico, Peru, or other regions where Cyclospora is endemic in water supplies
- You are immunocompromised — for example, due to chemotherapy, HIV treatment, or organ transplant medications
- A child under 5 or an adult over 65 in your household is experiencing these symptoms
Seeking care early is important for a specific reason: cyclospora infection cannot be cleared with rest and fluids alone. A physician must order the correct stool test — one that specifically looks for Cyclospora oocysts — confirm the diagnosis, and prescribe appropriate antibiotic treatment. Standard diarrhea tests typically do not detect this parasite.
Most cases begin with a primary care provider such as a family doctor or internist. If symptoms are prolonged, if the patient is immunocompromised, or if the first course of treatment fails, your doctor may refer you to a gastroenterologist or infectious disease specialist. ExpertZoom connects you with licensed physicians who can evaluate your symptoms and guide you through next steps — without waiting weeks for a specialist appointment.
How Doctors Treat Cyclosporiasis
The standard treatment for cyclosporiasis is trimethoprim-sulfamethoxazole (TMP-SMX), sold under brand names including Bactrim, Septra, and Cotrim. Typical dosing is twice daily for 7 to 10 days. Most patients experience clear improvement within that window.
Patients who cannot tolerate TMP-SMX — including those with sulfa allergies — may be prescribed ciprofloxacin or nitazoxanide (Alinia), though clinical evidence suggests these alternatives are less effective against Cyclospora. Adequate hydration is essential throughout recovery, and patients should expect residual fatigue for days to weeks after the active diarrhea phase resolves.
What You Can Do Right Now
While the CDC investigation continues, these steps reduce your risk:
- Wash all fresh produce thoroughly, even pre-washed or triple-washed packaged greens
- Cook fresh herbs if you are immunocompromised rather than adding them raw to dishes
- Avoid raw produce of uncertain origin at catered events, restaurant salad bars, or buffets during active outbreak periods
- Monitor the CDC Cyclosporiasis surveillance page for updated case counts, state breakdowns, and any food source identification as the investigation progresses
If you have eaten fresh herbs or leafy salad greens over the past two to four weeks and have developed any of the symptoms described above — particularly the characteristic watery diarrhea that worsens and then temporarily improves — do not dismiss it as ordinary stomach trouble. Ask your doctor specifically about Cyclospora testing.
For related foodborne illness guidance, the E. Coli Outbreak in Raw Cheese 2026 article covers another active 2026 food safety alert and explains when symptoms require emergency care. Consumer rights during product recalls are detailed in this guide on FDA Salmonella recalls and your legal options.
