The First Reported Outbreak of Diarrheal Illness Associated with Cyclospora in the United States

15 September 1995 | Volume 123 Issue 6 | Pages 409-414

Objective: To investigate and characterize the epidemiology of a diarrheal outbreak associated with a potentially new pathogen, Cyclospora species (previously referred to as Cyanobacteria [blue-green algae]-like bodies).

Design: Three retrospective cohort studies supported by laboratory studies, environmental investigation, and community surveillance.

Setting: A hospital in Chicago.

Participants: Housestaff physicians and hospital administrative staff.

Measurements: Identification of clinical features associated with illness and potential risks for acquisition of infection.

Results: Illness was characterized by watery diarrhea, abdominal cramping, decreased appetite, and low-grade fever. Symptoms typically occurred in a distinctive cycle of remissions and exacerbations 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 to 10 µ m in diameter, that were identified as Cyclospora organisms. The organisms disappeared by 9 weeks after onset of illness in the 7 patients from whom follow-up specimens were obtained. Epidemiologic studies implicated tap water from a physicians' dormitory as the most likely source of the outbreak. Environmental investigation suggested that stagnant water in a storage tank may have contaminated the water supply after a pump failure.

Conclusions: This is the first reported outbreak of diarrhea associated with Cyclospora in the United States. Cyclospora may be a human enteric pathogen able to produce bouts of acute and relapsing diarrhea, and it should be considered in assessments of patients with unexplained, prolonged diarrheal illness.

Author and Article Information

From the Centers for Disease Control and Prevention, Atlanta, Georgia.
Acknowledgments: The authors thank Elena Dacumos and Elvira Azarcon, MEd, for assistance with data collection; Russell J. Martin, DVM, MPH, and Carl Langkop, MSPH, of the Illinois Department of Public Health for assistance with the investigation and manuscript review; Kim R. Fox with the United States Environmental Protection Agency for assistance in evaluating the water system; Rebecca Wurtz, MD, of Cook County Hospital, and Eric Mintz, MD, MPH, with the Centers for Disease Control and Prevention, for additional assistance subsequent to the investigation; and staff of the City of Chicago Department of Water, the Illinois Department of Public Health, the Illinois Environmental Protection Agency, and the United States Environmental Protection Agency for their assistance.
Requests for Reprints: Philip Huang, MD, MPH, Bureau of Chronic Disease Prevention and Control, Texas Department of Health, 1100 West 49th Street, Austin, TX 78756.
Current Author Addresses: Dr. Huang: Bureau of Chronic Disease Prevention and Control, Texas Department of Health, 1100 West 49th Street, Austin, TX 78756.