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Cyclosporiasis is an intestinal illness caused by the microscopic parasite Cyclospora cayetanensis.

People can become infected with Cyclospora by consuming food or water contaminated with the parasite. People living or traveling in countries where cyclosporiasis is endemic may be at increased risk for infection.

Image: Infected people shed unsporulated (non-infective; immature) Cyclospora cayetanensis oocysts in their stool; immature oocysts usually require at least 1 week under favorable laboratory conditions to sporulate (become infective). An unsporulated oocyst, with undifferentiated cytoplasm, is shown (far left), next to a sporulating oocyst that contains two immature sporocysts (A). An oocyst that was mechanically ruptured has released one of its two sporocysts (B). One free sporocyst is shown as well as two free sporozoites, the infective stage of the parasite (C). Credit: CDC/DPDM.