The results for the daily probability of illness are calculated according to Equation (7). Moreover, the annual probability of illness is calculated according to Equation (8). The results are summarized in Table 7. The average probability of illness per time (Pill/time) for E. coli and norovirus was estimated at 3.42 × 10−14 and 3.05 × 10−15, respectively, morbidity for E. coli being slightly higher than for norovirus. By comparison of the different exposure routes, road flushing caused the highest morbidity due to microbial contamination. The prevalence of waterborne disease through river cleaning and boating were relatively low. Results for the annual probability of illness (Pill/y) were similar to the prediction of single morbidity (Pill/time). The average probability of illness of 5.55 × 10−12 per year was estimated to be attributed to E. coli, which was slightly higher than for norovirus. The annual morbidity due to road flushing was estimated at 9.06 × 10−12, which was much higher than the values estimated for the other two pathways.

Table 7

Results of morbidity calculation

E. coliNorovirusAverage
Pill/time
River cleaning 8.61 × 10−16 3.59 × 10−17 4.48 × 10−16
Boating 8.61 × 10−16 3.59 × 10−17 4.48 × 10−16
Road flushing 1.01 × 10−13 9.08 × 10−15 5.49 × 10−14
Average 3.42 × 10−14 3.05 × 10−15
Pill/y
River cleaning 3.55 × 10−14 1.78 × 10−14
Boating 1.32 × 10−14 6.61 × 10−15
Road flushing 1.66 × 10−11 1.50 × 10−12 9.06 × 10−12
Average 5.55 × 10−12 5.00 × 10−13
E. coliNorovirusAverage
Pill/time
River cleaning 8.61 × 10−16 3.59 × 10−17 4.48 × 10−16
Boating 8.61 × 10−16 3.59 × 10−17 4.48 × 10−16
Road flushing 1.01 × 10−13 9.08 × 10−15 5.49 × 10−14
Average 3.42 × 10−14 3.05 × 10−15
Pill/y
River cleaning 3.55 × 10−14 1.78 × 10−14
Boating 1.32 × 10−14 6.61 × 10−15
Road flushing 1.66 × 10−11 1.50 × 10−12 9.06 × 10−12
Average 5.55 × 10−12 5.00 × 10−13

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