HIV/AIDS News & Information

Event-associated clusters: In the index cluster, 35 of the 49 guests became ill (attack rate 71%). The median incubation pe­riod was eight days (range six to 13 days). Only symptomatic persons submitted stool specimens for laboratory testing, of whom 13 (59%) of the 22 were positive for cyclospora oocysts. The epidemic curve (Figure 1) was consistent with a point- source outbreak. No secondary cases were identified. Analyses of food exposures (Table 1) showed that the strawberry flan with raspberries and blueberries was the only food item sig­nificantly associated with illness (relative risk2.16,P=0.02).

By the end of July 1996, enhanced cluster surveillance identified six additional event-associated clusters of cases. All seven clusters are summarized in Table 2. The events occurred from May 11 through June 14, 1996. Of the 213 persons at­tending these seven events, 164 (77%) were interviewed. Among these, 20 laboratory-confirmed and 72 additional clinically defined cases of cyclosporiasis were identified. The overall attack rate was 56% (94 of 168). Cluster-specific attack rates ranged from 30% to 71%, and the median of the cluster- specific incubation periods was eight days. The incubation pe­riod for all 94 individual cases varied from two to 14 days.

Figure 1) Epidemic curvefor the index Ontario cyclosporiasis cluster, event data, May 11, 1996 (n=35 cases)

For all events, food recall histories indicated that various mixtures of raspberries, strawberries, blackberries and blue­berries were served. Raspberries were definitely not served at only one event (#3), an event at which blackberries from Gua­temala were served. The tracebacks that were well docu­mented demonstrated that raspberries served at events #1 and #6 originated from the same Guatemalan exporter and the blackberries from event #3 originated from another Gua­temalan exporter. Although tracebacks for the other events did not fulfill the criteria of being well documented, only ber­ries from outside Canada were available during the outbreak period.

TABLE 1 Food exposures and risk of developing illness in the index cluster in an outbreak of cyclosporiasis in Ontario in 1996

Sporadic cases: From May 1,1996, through July30,1996,140 sporadic cases were reported to the Ontario Ministry of Health. For the 131 cases for whom sex and age information was avail­able, the median age was 46 years (range 12 to 85 years) and 47% (n=62) were male. Public health unit personnel completed ques­tionnaires for 74 sporadic cases. No cases were hospitalized, nor were there any reported deaths. The proportion of sporadic cases who, during the two weeks before illness onset, reportedly ate raspberries was 42% (30 of 72), strawberries 78% (56 of 72), blueberries 24% (17 of 70) and blackberries 7% (five of 69). Case-control study: Twenty-six of the 140 sporadic cases and 52 controls were interviewed for the case-control study. Thirty-eight per cent (n=10) of the cases and 33% (n=17) of controls were men. The median ages of the cases and controls were 42 years (range 19 to 76 years) and 41 years (range 18 to 87 years), respectively. Cases were significantly more likely than their matched controls to have completed postsecondary educa­tion (matched odds ratio [MOR] = 7.33; 95% CI 1.89 to 28.0).
Most reliable pharmacy can offer cialis 200mg always charging you a lot less

TABLE 2 Summary of the seven clusters of cyclosporiasis in Ontario, 1996 (by event date)