The return of Cyclospora in 1997: Another outbreak of cyclosporiasis in North America associated with imported raspberries

Background: In the spring of 1996, an outbreak of cyclosporiasis associated with fresh Guatemalan raspberries occurred in the United States and Canada . Another multistate outbreak of cyclosporiasis occurred in North America i n the spring of 1997. Objective: To identify the vehicle of the outbreak that occurred in the spr ing of 1997. Design: Retrospective cohort studies of clusters of cases associated with e vents (such as banquets) and traceback investigations of sources of implica ted produce. Setting: United States and Canada. Patients: Persons who attended events associated with clusters of cases of cyclosporiasis. Measurements: identification of clinically defined or laboratory-confirmed cases of cyclosporiasis and risk factors for infection. Results: 41 clusters of cases were reported in association with events held from 1 April through 26 May in 13 U.S. states, the District of Columbia, a nd 1 Canadian province. The clusters comprised 762 cases of cyclosporiasis, 192 (25.2%) of which were laboratory confirmed. In addition, 250 laborator y-confirmed sporadic cases were reported in persons who developed gastroint estinal symptoms from April through 15 June, for a total of 1012 cases. Fre sh raspberries were the only food common to all 41 events and were the only type of berry served at 9 events (22.0%). Statistically significant associ ations between consumption of raspberry-containing items and cyclosporiasis were documented for 15 events (40.5% of 37), For 31 of the 33 events with well-documented traceback data, the raspberries either definitely came from Guatemala (8 events) or could have come from Guatemala (23 events). The mo de of contamination of the raspberries remains unknown. The outbreak ended shortly after the exportation of fresh raspberries from Guatemala was volun tarily suspended at the end of May 1997. Conclusions: Similar multistate, multicluster outbreaks of cyclosporiasis a ssociated with consumption of Guatemalan raspberries have occurred in conse cutive years. These outbreaks highlight the need for better understanding o f the biology and epidemiology of Cyclospora cayetanensis and for stronger prevention and control measures to ensure the safety of produce eaten raw.