[Evaluation of microbial indicators of health risk related to river swimming places]

A retrospective follow-up study was conducted among 5,737 tourists in 8 holiday camps, during the 1986 summer, in the Ardèche river basin, in order to study the relationship between the bacteriological water quality and the morbidity that occurred to swimmers. Total morbidity was more frequent among bathers than non-bathers (Risk Ratio = 1.7 [95% confidence interval = 1.4-2.1]); gastro-intestinal illness was the major type of morbidity (RR = 2.8 [1.8-4.4] for "objective gastro-intestinal diseases). After screening for the germs that were best correlated with gastro-intestinal and skin diseases, using simple linear regression, logistic regression models allowed confirmation that fecal streptococci best predicted gastro-intestinal morbidity; it significantly exceeded the risk observed among non-bathers above a concentration of 20 SF/100 ml ("objective" gastro-intestinal morbidity). The relationship with fecal coliforms was less clear. However, they are good indicators of skin diseases risk. These results should help re-evaluation of the current microbiological standards concerning recreational waters.