Public Health and Water Quality Significance of Viral Diseases Transmitted by Drinking Water and Recreational Water

A review of the available information from case and outbreak reports and the results of prospective and retrospective studies revealed that the potential for the spread of viral diseases by the use of fecally contaminated drinking and recreational water has only been realized for infectious hepatitis and viral gastroenteritis. These two, however, are the most serious and prevalent, respectively, of the water-related diseases. A model is described for predicting the beach specific, swimming-associated rates and annual number of cases of gastroenteritis. The inputs are the swimming-associated, gastroenteritis rate-bathing water enterococcus density regression equation developed from the USEPA prospective epidemiologic-microbiologic studies and the distribution of enterococcus density estimates and annual number of swimmers at the beach in question. In general, the gastroenteritis rates predicted from the enterococcus model were less than those from the corresponding E. coli model. Detectable rates at the 75 percentile level and rates approaching or exceeding 5/1000 swimmers at the 90 percentile level were predicted for 7 and 14, respectively, of the 87 sampling station-beach associations. All but one of the fourteen stations were potentially impacted by known municipal wastewater discharges and two of the associated beaches were posted as unsafe for swimming. The inapplicability of the model to beaches impacted with small, immediate sources of fecal wastes or stormwater run-off is noted. The limitations in the use of findings from the analysis of outbreak reports in the evaluation and establishment of water quality criteria and, hence, the need for prospective, drinking water and shellfish epidemiological studies is discussed. The need for such studies also derives from the results of the bathing beach study in that they suggest that cases of gastroenteritis are occurring with acceptable drinking and shellfish growing waters. The need for tissue culture enumerative methods for the viral gastroenteritis agents and methodology for determining the biological decay coefficients for these agents and their indicators is noted.