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Update: Outbreaks of Cyclosporiasis -- United States and Canada, 1997

Since April 1997, CDC has received reports of outbreaks of cyclosporiasis in the United States and Canada (1,2). As of June 11, there have been 21 clusters of cases of cyclosporiasis reported from eight states (California, Florida, Maryland, Nebraska, Nevada, New York, Rhode Island, and Texas) and one province in Canada (Ontario). These clusters were associated with events (e.g., receptions, banquets, or time-place-related exposures {meals in the same restaurant on the same day}) that occurred during March 19-May 25 and comprise approximately 140 laboratory-confirmed and 370 clinically defined cases of cyclosporiasis. In addition, four laboratory-confirmed and approximately 220 clinically defined cases have been reported among persons who, during March 29-April 5, were on a cruise ship that departed from Florida. Approximately 70 laboratory-confirmed sporadic cases (i.e., cases not associated with events, the cruise, or recent overseas travel) have been reported in the United States and Canada. The most recent laboratory-confirmed sporadic case occurred in a person who had onset of symptoms on June 3.

Fresh raspberries were served at 19 of the 21 events and were the only food in common to all 19 events, which occurred in April and May. At six of the 19 events, raspberries were the only type of berry served or were served separately from other berries; at 13 events, raspberries were included in mixtures of various types of berries. Eating the food item that included raspberries was significantly associated with risk for illness for seven of the 15 events for which epidemiologic data are currently available (including for three of the events at which raspberries were not served with other types of berries) and was associated with illness but not significantly for six events (i.e., all or nearly all ill persons ate the berry item that was served). The raspberries reportedly had been rinsed in water at 10 (71%) of the 14 events for which such information is available. Guatemala has been identified as one of the possible sources of raspberries for all eight events for which traceback data are currently available (i.e., Guatemala was the source of at least one of the shipments of raspberries that could have been used) and as the only possible source for at least one of these events and perhaps for two others for which the traceback investigations are ongoing.

Fresh raspberries were not served at two events in restaurants in Florida that have been associated with clusters of cases of cyclosporiasis (persons were exposed on March 19 and April 10, respectively, in two different cities). The first cluster was associated with eating mesclun (also known as spring mix, field greens, or baby greens -- a mixture of various types of baby leaves of lettuce); the specific source of the implicated mesclun has not been determined. Mesclun also is suspected as the vehicle for the second cluster.

Reported by: E DeGraw, Leon County Health Dept, Tallahassee; S Heber, MPH, A Rowan, Florida Dept of Health. Other state, provincial, and local health depts. Health Canada. Office of Regulatory Affairs, and Center for Food Safety and Applied Nutrition, Food and Drug Administration. Div of Applied Public Health Training (proposed), Epidemiology Program Office; Div of Parasitic Diseases, National Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: The investigations described in this report indicate that fresh raspberries imported from Guatemala are the probable vehicle of infection for most of the outbreaks of cyclosporiasis identified in 1997. There is no evidence of ongoing transmission of Cyclospora in association with mesclun, which was the vehicle for one, and possibly two, early outbreaks in March and April. In the spring and summer of 1996, an outbreak of cyclosporiasis in the United States and Canada was linked to eating raspberries imported from Guatemala (3). However, the mode of contamination of the raspberries implicated in that outbreak was not determined -- in part because the methods for testing produce and other environmental samples for this emerging pathogen are insensitive and nonstandardized. No outbreaks of cyclosporiasis were reported in the United States in association with importation of raspberries from Guatemala during the fall and winter of 1996; however, cyclosporiasis is highly seasonal in some countries.

After the outbreak in 1996, the berry industry in Guatemala, in consultation with the Food and Drug Administration (FDA) and CDC, voluntarily implemented a Hazard Analysis and Critical Control Point system and improved water quality and sanitary conditions on individual farms (3). The occurrence of outbreaks in 1997 suggests either that some farms did not fully implement the control measures or that the contamination is associated with a source against which these measures were not directed.

At FDA's request, on May 30, 1997, the government of Guatemala and the Guatemalan Berries Commission announced their decision to voluntarily suspend exports of fresh raspberries to the United States (the last shipment was May 28). FDA is working with CDC, the government of Guatemala, and the Guatemalan Berries Commission to determine when exports can resume (4). Because of the relatively short shelf life, few, if any, fresh raspberries grown in Guatemala are available now for purchase and consumption in the United States. Cyclospora oocysts, like the oocysts of other coccidian parasites, are expected to be inactivated by temperature extremes (e.g., pasteurization or commercial freezing processes). The minimum time and temperature conditions required to inactivate Cyclospora oocysts by heating or freezing have not yet been determined.

Although exports of fresh raspberries from Guatemala to the United States have been suspended until further notice, cases of cyclosporiasis that are attributable to consumption of raspberries may continue to be identified by health-care providers and health departments. The average incubation period for cyclosporiasis is 1 week; if not treated with trimethoprim-sulfamethoxazole (5), illness can be protracted, with remitting and relapsing symptoms. Health-care providers should consider Cyclospora infection in persons with prolonged diarrheal illness and specifically request laboratory testing for this parasite. Cases should be reported to local and state health departments; health departments that identify cases of cyclosporiasis should contact CDC's Division of Parasitic Diseases, National Center for Infectious Diseases, telephone (770) 488-7760. Newly identified clusters of cases should be investigated to identify the vehicles of infection and to trace the sources of implicated foods.

References

  1. CDC. Outbreaks of cyclosporiasis -- United States, 1997. MMWR 1997;46:451-2.

  2. CDC. Update: outbreaks of cyclosporiasis -- United States, 1997. MMWR 1997;46:461-2.

  3. Herwaldt BL, Ackers M-L, Cyclospora Working Group. An outbreak in 1996 of cyclosporiasis associated with imported raspberries. N Engl J Med 1997;336:1548-56.

  4. Food and Drug Administration. Outbreak of cyclosporiasis and Guatemalan raspberries. Rockville, Maryland: US Department of Health and Human Services, Public Health Service, Food and Drug Administration, June 10, 1997. (Talk Paper T97-22).

  5. Hoge CW, Shlim DR, Ghimire M, et al. Placebo-controlled trial of co-trimoxazole for Cyclospora infections among travellers and foreign residents in Nepal. Lancet 1995;345:691-3.




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