THE FIRST REPORTED OUTBREAK OF DIARRHEAL ILLNESS ASSOCIATED WITH CYCLOSPORA IN THE UNITED-STATES

Objective: To investigate and characterize the epidemiology of a diarr heal outbreak associated with a potentially new pathogen, Cyclospora s pecies (previously referred to as Cyanobacteria [blue-green algae]-lik e bodies). Design: Three retrospective cohort studies supported by lab oratory studies, environmental investigation, and community surveillan ce. Setting: A hospital in Chicago. Participants: Housestaff physician s and hospital administrative staff. Measurements: Identification of c linical features associated with illness and potential risks for acqui sition of infection. Results: Illness was characterized by watery diar rhea, abdominal cramping, decreased appetite, and low-grade fever. Sym ptoms typically occurred in a distinctive cycle of remissions and exac erbations lasting up to several weeks. Stool cultures and examinations for known ova and parasites were negative. Microscopic examination of stool specimens from 11 ill persons showed many spherical bodies, 8 t o 10 mu m in diameter, that were identified as Cyclospora organisms. T he organisms disappeared by 9 weeks after onset of illness in the 7 pa tients from whom follow-up specimens were obtained. Epidemiologic stud ies implicated tap water from a physicians' dormitory as the most like ly source of the outbreak. Environmental investigation suggested that stagnant water in a storage tank may have contaminated the water suppl y after a pump failure. Conclusions: This is the first reported outbre ak of diarrhea associated with Cyclospora in the United States. Cyclos pora may be a human enteric pathogen able to produce bouts of acute an d relapsing diarrhea, and it should be considered in assessments of pa tients with unexplained, prolonged diarrheal illness.