Study of the association between waterborne diseases and microbial water quality in Israel

Background. The purpose of this project was to look for an association between microbial quality of drinking water and those gastrointestinal diseases that are known to be also waterborne. Methods. For this purpose available databases of the Israeli Ministry of Health were used: (1) Registry of notifiable diseases and (2) microbial quality of drinking water. The association was examined by regressing incidence rates of salmonellosis, shigellosis, and hepatitis on three measures of microbial water quality and calculating the coefficient of determination (r²). Analysis was carried out for the years 1985-1992. Results. Significant dependence of disease incidence on water quality was found for 1988 and, for hepatitis, also for 1989-92. This dependence is shown to be the result of the coincidence of high disease rate with high proportion of polluted water samples in two small subdistricts. Conclusions. The general lack of dependence of morbidity on water quality suggests that the water route contributes only slightly to these diseases in Israel. For a more meaningful analysis, a higher geographic resolution of morbidity reporting is recommended.