Many common forms of recreation involve water exposure. Pathogens in water infect susceptible humans by multiple routes: through skin and mucous membranes, via inhalation of aerosols, aspiration, and ingestion. Clinical manifestations of these infections range from superficial skin lesions to fatal, systemic infections. The survival of many water-associated pathogens is influenced by climate, season, other environmental conditions, and the level of sanitation. The types and abundance of organisms vary depending on the salinity, pH, temperature, and other characteristics of the water. Hence, many are found only or primarily in certain geographic regions or during some seasons of the year. The risk of infection by waterborne pathogens is a function of the duration and type of exposure, concentration density of organisms in water, and host immunity. This chapter describes the types of pathogens, geographic distribution, sources and routes of transmission, clinical presentations, and management of water-associated infections. Water can also be a source of toxins, including heavy metals. Oceans and beaches are the sites of marine envenomations. These topics are beyond the scope of this chapter.

United States residents make approximately 360 million visits to recreational water venues annually. Thus, outbreaks of infections related to recreational water exposures are common. In the United States in 2003–2004, for example, 62 waterborne disease outbreaks in 26 states were reported to the Centers for Disease Control and Prevention (CDC).