Cyclosporiasis is a foodborne illness caused by the microscopic parasite Cyclospora cayetanensis, which is transmitted through feces-contaminated food and water. The parasite must sporulate in the environment for 1–2 weeks before becoming infectious, making direct person-to-person transmission unlikely, and symptoms typically appear about a week after ingestion. The primary symptom is watery diarrhea, often accompanied by cramps, fatigue, and weight loss; while many cases are mild, severe dehydration can be fatal, especially in infants and immunocompromised individuals. Although infections occur worldwide, they are most common in tropical regions, and since the 2010s, seasonal US outbreaks have been linked to contaminated fresh produce like leafy greens, basil, and berries. Diagnosis can be challenging but is confirmed using PCR-based DNA tests or acid-fast staining of stool samples.