Although our definition of HCGI was patterned after the work of Payment et al.
Payment reported an attributable fraction of 35% (of HCGI attributable to drinking water consumption); our study's point estimate of the attributable fraction was 24%.
If a study were designed with 80% power to detect a true reduction in HCGI to 1.
The relative rates of illness overall were very similar to those reported in an earlier, larger randomized trial in Canada, which did report statistically significant differences in HCGI between the groups.
The impact of varying this estimate to 10% of bathers in the water despite beach closures was examined in terms of total expected HCGI cases over the study period.
Application of Cabelli's relationship to total number of exposures yielded 95,010 cumulative HCGI cases over the study period (Figure 5A).
Application of Cabelli's relationship resulted in peak attack rates of approximately 600 cases per day in summer months, with the maximum number of HCGI cases at 665.
Figure 6 illustrates that HCGI attack rates are highly influenced by the enterococcus--HCGI risk relationships applied to the exposure data.
Figure 7 shows a comparison of HCGI rates under the clustered and uniform bather distribution scenarios.
1% increase in the total number of HCGI cases over the study period.
95,010 HCGI cases resulted with no bathing activity assumed during beach closures, whereas 95,117 illness cases resulted when 10% of beachgoers bathed during beach closure days.
The results suggest that the majority of HCGI cases occur in the summer months and, to a lesser degree, in the late spring, regardless of bather distribution.