National Parasites Outbreak: Cyclosporiasis

The Stomach Bug the Standard Test Misses

By Cayla McGrath

Three weeks of watery, cramping diarrhea. A few days that feel terrible, then a few days that feel almost like recovery — then back again. The standard stool test came back clean. The problem may not be that the test was negative. The problem may be that the test wasn’t looking for the right thing.

Cyclospora cayetanensis — the parasite behind cyclosporiasis — does not show up on a routine stool culture. It doesn’t appear on a standard ova and parasite exam either, unless the lab is specifically running a modified acid-fast stain, or using a PCR panel that names Cyclospora as a target. Order the standard panel and you will miss it. The patient keeps being told it’s probably viral, give it time, and keeps feeling this way through weeks of illness that could have been resolved.

This is happening more than most people realize. The CDC tracks cyclosporiasis outbreaks, and the 2026 case counts are coming in above recent baseline in several regions. The linked produce: imported fresh herbs, leafy greens, raspberries — the same categories tied to previous multi-state clusters.

Why it gets missed

Most acute diarrhea gets the same initial workup: a routine stool culture, maybe an ova and parasite exam. For most causes of infectious diarrhea, this is the right starting point. Cyclospora is the exception the standard order set was not built to catch.

Part of why it keeps slipping past is the presentation. Cyclosporiasis doesn’t always announce itself dramatically. The onset is often gradual. The diarrhea is watery and cramping rather than bloody. The characteristic relapsing pattern — feeling somewhat better, then declining again — looks from the outside exactly like a slow-resolving viral illness. Add in fatigue, loss of appetite, and sometimes modest weight loss, and there’s nothing in the clinical picture to distinguish it from ‘a stomach bug that’s taking too long to clear’ unless someone orders the right test.

Cyclospora is also seasonal. U.S. outbreaks cluster in late spring and summer, tied to the import season for the produce categories most commonly linked. If a prolonged GI illness is happening in May through August, Cyclospora belongs on the differential.

What actually treats it

When cyclosporiasis is confirmed, the standard treatment is trimethoprim-sulfamethoxazole (TMP-SMX — the antibiotic in Bactrim/Septra) for seven to ten days for most adults. It clears the infection for the majority of patients within that window. Jase has this medication as an add-on to the JaseCase as well as standard in the JaseGo travel kit. 

The complication worth knowing about: sulfa allergies. TMP-SMX is not an option for patients with sulfa hypersensitivity, and the alternatives — ciprofloxacin, nitazoxanide — are real options that clinicians use, but they’re not as well-studied specifically for cyclosporiasis. Raise this with your provider if a sulfa allergy is in the picture.

What this means practically

If a diarrheal illness has been going on for more than two weeks — especially with the cramping, relapsing pattern, fatigue, or unexplained weight loss — it’s reasonable to ask your provider whether the workup included a test specifically for Cyclospora. Not just a routine stool culture. The specific test: a modified acid-fast stain, or a PCR panel that includes Cyclospora as a named target.

Two corrections worth making: thorough washing of produce reduces risk from many foodborne pathogens but doesn’t reliably eliminate Cyclospora oocysts, which can adhere tightly to produce surfaces. And unlike norovirus, Cyclospora does not spread easily from person to person. A cluster in a household almost certainly means a shared food source, not person-to-person transmission.

The real frame here is informed patience: knowing when ‘give it more time’ has gone on long enough, and knowing what question to ask when it has. ‘Did you test specifically for Cyclospora?’ is a short sentence that can change the outcome significantly.

Where JaseCase fits

Ciprofloxacin — one of the three antibiotics in the JaseCase — is one of the alternative agents used for cyclosporiasis when TMP-SMX can’t be given. This is a good example of why knowing what a drug covers matters: cipro has a specific but narrower role in this indication, and TMP-SMX remains the standard treatment. For cyclosporiasis specifically, the path runs through diagnosis first: ask for the specific test, get the confirmation, and then get the appropriate treatment from your provider.

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Cayla McGrath is a content strategist with Jase Medical. This post is for informational purposes only and does not constitute medical advice. Always consult a licensed healthcare provider before using any prescription medication.