[Evaluation of microbial indicators of health risk related to river swimming places]. / Evaluation des indicateurs microbiens du risque sanitaire lié aux baignades en rivière.

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.

Epidemiological significance of microbiological pollution criteria for river recreational waters.

A retrospective follow-up study was conducted during the summer of 1986 in the French Ardèche basin in order to assess the relationship between swimming-related morbidity and the bacteriological quality of the recreational water. 5737 tourists in eight holiday camps were questioned as to the occurrence of illness and their bathing habits during the week preceding the interviews. The rate-ratio contrasting swimmers and non-swimmers for total morbidity is 2.1 (1.8-2.4) = 95% confidence interval); gastrointestinal illness is the major type of morbidity and differs significantly between the two groups (RR = 2.4 (1.9-3.0) for total gastrointestinal cases; RR = 2.3 (1.7-3.2) for 'objective' gastrointestinal cases). Faecal streptococci (FS) are best correlated to gastrointestinal morbidity, using direct linear regression models. Faecal coliforms (FC) are not as good predictors of the risk. The concentration of faecal streptococci above which the 'objective' gastrointestinal morbidity among bathers is significantly greater than among non-bathers is 20 FS/100 ml. Swimmers suffer skin ailments much more frequently than non-swimmers (RR = 3.7 (2.4-5.7]; although the relationship may be artefactual, this type of morbidity is well correlated with the concentration of faecal coliforms, aeromonas and pseudomonas. This study provides epidemiological data on which to base microbiological standards for river recreational waters dependent on what might be considered as an 'acceptable' risk.