Disease outbreaks associated with untreated recreational water use.

Annual overviews of waterborne disease outbreaks associated with untreated recreational water use provided by authorities responsible for bathing-water quality and public health in The Netherlands revealed 742 outbreaks during 1991-2007 mainly comprising of skin conditions (48%) and gastroenteritis (31%) and involving at least 5623 patients. The number of outbreaks per bathing season correlated with the number of days with temperatures over 25°C (r=0.8-0.9), but was not reduced through compliance with European bathing-water legislation (r=0.1), suggesting that monitoring of faecal indicator parameters and striving for compliance with water-quality standards may not sufficiently protect bathers. Bathing sites were prone to incidental faecal contamination events or environmental conditions that favoured the growth of naturally occurring pathogens. Identification of all possible contamination sources, awareness of changes that might negatively affect water quality, and provision of adequate information to the public are important preventive measures to protect public health.