Update: Outbreaks of Cyclospora cayetanensis Infection -- United States and Canada, 1996

Since May 1996, CDC has received reports of clusters and sporadic cases of infection with the parasite Cyclospora cayetanensis that occurred in May and June in the United States and Canada (1). This report describes preliminary findings of an investigation by the New Jersey Department of Health and Senior Services (NJDHSS) and updates the findings of other ongoing investigations. New Jersey

During June 17-26, 1996, NJDHSS received reports of 42 sporadic cases of laboratory-confirmed Cyclospora infection (by light microscopic examination of a stool specimen) among New Jersey residents. To assess possible risk factors for infection among persons with sporadic cases, NJDHSS conducted a case-control study. A case was defined as laboratory-confirmed Cyclospora infection and symptoms of gastroenteritis (e.g., diarrhea) with onset during May 1-June 20, 1996, in a New Jersey resident aged greater than or equal to 18 years. Two age-matched (plus or minus 10 years) controls (aged greater than or equal to 18 years) were selected by random-digit dialing; to be eligible, controls could not have had loose stools during the 2-week period before onset of symptoms for the referent case-patient (i.e., the period of interest). In addition, case-patients and matched controls must have been in New Jersey during the period of interest and not have traveled outside the United States or Canada during the month before symptom onset. Investigators interviewed 30 case-patients and 60 controls by telephone and used a standardized questionnaire that asked about possible exposures (including consumption of 17 fruits and 15 vegetables, water and soil exposures, and animal contact) during the period of interest.

Case-patients and controls were similar by age (median age of case-patients: 47.5 years {range: 20-81 years}), sex, and educational level. Twenty (69%) of 29 case-patients and four (7%) of 60 controls had eaten raspberries. In multivariate conditional logistic regression analysis, only consumption of raspberries was significantly associated with illness (odds ratio and 95% confidence interval were undefined because of a denominator of 0, p less than 0.001 {computed using the score test}). Consumption of strawberries was not significantly associated with illness. Other Investigations

Approximately 850 cases of laboratory-confirmed Cyclospora infection in persons residing in the United States and Canada whose onset of illness was in May and June 1996 have been reported to CDC and Health Canada. Approximately 14% of all cases have been reported from Ontario, Canada; nearly all (approximately 99%) of the other cases have been reported from states east of the Rocky Mountains. Fourteen states, the District of Columbia, and Ontario are each investigating clusters of cases related to specific events (e.g., a luncheon) and/or at least 30 sporadic cases (i.e., not related to any identified event). Six other states have each reported less than or equal to 10 sporadic cases. Most sporadic and event-related cases have occurred in immunocompetent adults. Fifteen case-patients have been hospitalized, but no deaths have been reported. The most recent event associated with cases occurred on June 8 (i.e., exposure date), and the most recent laboratory-confirmed sporadic case occurred in a person with onset of symptoms on June 27.

With the possible exception of a few events for which limited information is available, raspberries were served at the 42 events under investigation. For 12 (29%) of the events, raspberries were either the only berry served or were served separately from other berries. Initial investigations of three events that occurred in May had attributed risk for Cyclospora infection to consumption of strawberries; however, further investigation indicated that raspberries and other berries also were served (one event) or may have been served (two events). Preliminary findings of case-control studies by health departments in Florida and New York City also indicate an association between consumption of raspberries and risk for Cyclospora infection.

The Food and Drug Administration (FDA), CDC, and other health and food-safety agencies in the United States and Canada are tracing the sources of the raspberries that were served at the events. Findings from the first 21 tracebacks completed by CDC and state agencies indicate that raspberries grown in some regions of Guatemala either definitely were or could have been served at each of these events; for 17 of these 21 events, the only source of raspberries was Guatemala. Efforts are ongoing to identify the specific source(s) of the raspberries and possible modes of contamination.

Reported by: Health Protection Br, Health Canada. J Hofmann, MD, Z Liu, MD, C Genese, MBA, G Wolf, MBA, W Manley, MA, K Pilot, E Dalley, MA, L Finelli, DrPH, Acting State Epidemiologist, New Jersey Dept of Health and Senior Svcs. Prevention Effectiveness Activity, Office of the Director, and Div of Field Epidemiology, Epidemiology Program Office; Foodborne and Diarrheal Diseases Br, Div of Bacterial and Mycotic Diseases, and Div of Parasitic Diseases, National Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: The multistate outbreak of infection with the emerging pathogen Cyclospora has been investigated by state and local health departments, CDC, health officials in Canada, and other organizations. Although the findings of these investigations have demonstrated consistent associations between risk for Cyclospora infection and antecedent consumption of raspberries, some case-patients have not reported raspberry consumption; this finding may reflect poor recall and, for some persons with cases not related to events, different sources of infection.

The preliminary investigations indicate that some regions of Guatemala were the most likely sources of the epidemiologically implicated raspberries. The growing season in Guatemala is ending, and recent imports of raspberries from that country have markedly decreased. The specific mode of contamination of the raspberries and whether contamination occurred in Guatemala or after the raspberries had been shipped from the country have not yet been determined. CDC, FDA, the government of Guatemala, growers, exporters, and trade associations are collaborating in ongoing investigations to evaluate these issues. Since the latter half of June, FDA has begun to examine shipments of raspberries from Guatemala for Cyclospora. Cyclospora oocysts have not been found on any of the raspberries that have been tested to date. FDA, CDC, and others are developing standardized methods for such testing and are evaluating their sensitivity.

As always, produce should be thoroughly washed before it is eaten. This practice should decrease but may not eliminate the risk for transmission of Cyclospora. Health departments that identify cases of Cyclospora infection should contact CDC's Division of Parasitic Diseases, National Center for Infectious Disease, telephone (770) 488-7760.

Reference

1. CDC. Outbreaks of Cyclospora cayetanensis infection -- United States, 1996. MMWR 1996; 45:549-51.

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