How The Cyclospora Parasite Spreads—And How To Protect Yourself

A parasite you've probably never heard of is sickening hundreds across the country — and the usual food safety rules might not be enough. Cyclospora cayetanensis, a microscopic parasite that causes the diarrheal illness cyclosporiasis, is spreading in an unusually large outbreak this summer, with cases reported in multiple states. Here's how it spreads, the symptoms to watch for, and the most effective ways to protect yourself.

The Centers for Disease Control and Prevention (CDC) is investigating a multistate outbreak of cyclosporiasis linked to fresh produce, though the exact source remains unconfirmed. As of mid-July 2026, at least 250 laboratory-confirmed cases have been reported across 18 states, with hospitalizations in several cases. While cyclospora outbreaks are not rare — they typically occur in late spring and summer when imported produce is in season — the scale and geographic spread of this year's outbreak have caught health officials' attention.

Cyclospora is not a bacterium or virus; it's a one-celled parasite that infects the small intestine. It is spread by ingesting food or water contaminated with the parasite's oocysts (immature eggs). Unlike many foodborne pathogens, cyclospora does not spread from person to person because the oocysts need time outside the body to become infectious. This means contaminated food or water is almost always the culprit. The most common vehicles are fresh produce — raspberries, basil, cilantro, snow peas, and lettuce — typically imported from tropical and subtropical regions where the parasite is endemic.

The incubation period averages seven days (range: 2 to 14 days), making it difficult for people to link their illness to a specific meal. Symptoms include watery diarrhea (often explosive), loss of appetite, weight loss, stomach cramps, bloating, nausea, and fatigue. Low-grade fever is possible but less common. Untreated cases can last several weeks to a month, and relapses are common, often triggered by stress or a return to a normal diet. Dr. Patricia Griffin, a CDC expert on foodborne diseases, notes that the illness can be particularly severe for immunocompromised individuals, young children, and the elderly.

Diagnosis requires a specialized stool test that is often not part of routine testing, which means many cases go undetected. The recommended treatment is a course of trimethoprim-sulfamethoxazole (TMP-SMX), an antibiotic combination. For those with sulfa allergies, alternative therapies are limited and less effective. Hydration is critical to manage the diarrhea.

Protecting yourself starts with recognizing that washing produce — even thoroughly — may not remove all cyclospora oocysts because they adhere tightly to surfaces. The CDC recommends cooking produce to an internal temperature of at least 145°F (63°C) to kill the parasite, or thoroughly washing produce under running water and scrubbing with a brush for firm produce like melons and cucumbers. However, for high-risk items like berries and leafy greens, the safest option is to cook them or purchase frozen versions that have been heated during processing. When traveling to countries where cyclospora is common (tropical and subtropical regions), drink bottled or boiled water and avoid fresh, uncooked produce from local markets.

This outbreak serves as a reminder that our global food supply chain brings risks from faraway pathogens into our kitchens. The cyclospora parasite does not respect borders, and the increasing volume of imported fresh produce means these outbreaks may become more frequent. As investigators work to trace the source, consumers should stay informed about recalls and advisories. Public health agencies emphasize that reporting symptoms promptly and providing a detailed food history to your doctor can help accelerate identification of contaminated foods.

The outlook: Expect the CDC to issue food safety alerts as the investigation progresses. If a common source is identified, a recall will follow. In the meantime, the best defense is a combination of careful food handling, cooking, and awareness. Cyclospora is preventable — but only if you know the right precautions.