SWIMMING-ASSOCIATED GASTROENTERITIS AND WATER QUALITY

A direct, linear relationship between swimming-associated gastrointestinal illness and the quality of the bathing water was obtained from a multi-year, multiple-location prospective epIdemIologic-mIcrobIologIc research program conducted in New York City, 1973–1975, Lake Pontchartrain, Louisiana, 1977–1978, and Boston, Massachusetts, 1978. Several microbial indicators were used in attempting to define the quality of the water; and, of those examined, enterococci showed the best correlation to total and “highly credible” gastrointestinal symptoms. The frequency of gastrointestinal symptoms also had a high degree of association with distance from known sources of municipal wastewater. A striking feature of the relationship was the very low entero coccus and Escherlchla coil densities In the water (10/100 ml) associated with appreciable attack rates (about 10/1000 persons) for “highly credible” gastrointestinal symptoms. Moreover, the ratio of the swimmer to nonswimmer symptom rates indicated that swimming in even marginally polluted marine bathing water is a significant route of transmission for the observed gastroenteritis.