There is currently a large outbreak of cyclosporiasis, a foodborne illness, that’s making headlines. Here’s a brief look at what you need to know.
There is a very large outbreak of cyclosporiasis underway. Current reports are concentrated in southeast Michigan and northwest Ohio – Michigan has reported over 700 cases since late June, which is approximately 14 times the state's annual average. Cases have been identified in at least 18 states, including New York, North Carolina, Indiana, and Texas, with an unofficial national count (based on state reports) likely exceeding 1,200. It's not yet confirmed whether these state clusters share a common source.
Cyclospora cayetanensis is a microscopic parasite that inhabits the small intestine. Infection begins when someone ingests contaminated food or water. Fresh produce like herbs, leafy greens, fruits, etc. are most commonly implicated. Unlike some other stomach bugs you may be familiar with, like norovirus, cyclosporiasis is not transmitted through direct contact with e.g., an infected household member.
Symptoms include prolonged watery diarrhea, fatigue, loss of appetite, weight loss, abdominal cramping, bloating, nausea, and low-grade fever. These symptoms typically develop one week after exposure. Cyclosporiasis often follows a relapsing pattern. If untreated, symptoms improve and then return over several weeks or months. This pattern, combined with the fact that routine stool tests don’t detect this parasite, can lead to missed diagnoses or misdiagnoses like irritable bowel syndrome.
The parasite typically contaminates produce at the farm or irrigation source, and then the product is distributed to stores and purchased by consumers. U.S. outbreaks are commonly associated with imported fresh produce, including bagged salads, leafy greens, fresh basil, fresh cilantro, and raspberries.
No specific food source has been identified or recalled as of this date. State health departments, the CDC, and the FDA are still working to identify the source.
If you're higher-risk
Cyclosporiasis is highly unpleasant but often self-limiting in healthy adults. For older adults and people with immunocompromise, though, infection can be dangerous. People at higher risk include, for example, chemotherapy patients, solid organ transplant recipients, or others on immunosuppressive medications.
For those high risk populations, the illness may be more severe, prolonged, and prone to relapse. Chronic diarrhea increases the risk of dehydration and electrolyte imbalances, which can complicate heart, kidney, or other underlying conditions. However, the infection is treatable with appropriate medical care.
What to do
Until a source is identified, readers who are more cautious or at higher risk may want to limit foods historically linked to these outbreaks, like leafy greens and bagged salads, fresh herbs like basil and cilantro, raspberries, snow peas, and green onions. But to be clear, no specific source has been identified, so this option is a best guess for precautions.
Evidence on the effectiveness of rinsing produce to prevent cyclosporiasis is sparse. From my quick review, I came to the conclusion that rinsing can help to reduce risk, but not reliably because the oocysts are sticky. I wasn’t able to find clear guidance on veggie sprays, but the parasite is quite hardy and resistant to chlorine sanitization, so I think they are unlikely to work.
Cooking does eliminate it, so cooked vegetables are a safer choice while the investigation continues.
Persistent watery diarrhea accompanied by fatigue and appetite loss should prompt a visit to the doctor, particularly with dehydration (reduced urination, dizziness on standing, dry mouth, or feeling faint). Routine stool tests do not detect Cyclospora, so clinicians must specifically request testing for this parasite. More information for clinicians is available at our sister site, FOI Clinical.
I'll keep you updated as the source investigation continues.