Cyclospora cayetanensis is a protozoan parasite that causes cyclosporiasis, a diarrheal disease transmitted through the fecal-oral route by consuming contaminated food or water. First reported in Papua New Guinea in 1979, the pathogen was formally named in the early 1990s after the Cayetano Heredia University in Peru, where foundational research occurred. The parasite invades the small intestine's jejunum, but its oocysts require days to weeks to become infectious outside the host, so person-to-person spread is rare—a key difference from Cryptosporidium parvum. Although once unknown in developed nations, it has become a notable cause of foodborne outbreaks linked to imported fruits and vegetables, endemic diarrhea in tropical countries, and traveler's diarrhea globally.