Cyclosporiasis refers to infection by Cyclospora, a microscopic, single-celled parasite that infects the human intestine. This parasite is a member of the group of protozoa known as coccidia, to which Cryptosporidia also belongs. This group of parasites infects the human intestine, and causes chronic recurrent infections in those with altered immunity or AIDS>. Even in people with normal immune function, Cyclopsora can cause prolonged bouts of diarrhea and other gastrointestinal symptoms.

Until recently, Cyclospora was considered to be a form of algae. The parasite causes a common form of waterborne infectious diarrhea throughout the world. Just how the parasite gets into water sources is not yet clear. It is known that ingestion of small cysts in contaminated water leads to disease.

Symptoms begin after an incubation period of about a day or so following ingestion of cysts. A brief period of flu-like illness characterized by weakness and low-grade...