On tap: recreational waterborne disease at an all-time high

Levels of recreational waterborne disease are at their highest since reporting began in 1978, suggesting the need for interventions aimed at reducing risks in natural and treated water systems. More outbreaks are reported related to recreational  waterborne diesease than drinking water sources. Every two years the Centers for Disease Control and Prevention (CDC) publishes a report on waterborne disease outbreaks in the US. These surveillance summaries provide the single most complete source of data on documented drinking and recreational waterborne illnesses since 1971 and 1978, respectively. The most recent surveillance summary (Yoder et al., 2008) describes 78 reported recreational water outbreaks from 2005-2006, some with fatal consequences.

Recreational waterborne disease

From 2005-2006, 31 states in the US reported a totar of 78 outbreaks due to recreational water exposure. The source of exposure is most commonly ingestion (61.5 percent) but inhalation (12.8 percent), direct skin contact (10.3 percent) and mixed exposure routes (11.5 percent) and other (3.8 percent) are also confirmed. Events range from cases of enteric illness, ailments, skin infections and irritations, hospitalization and death. Of the 4,412 persons reporting illness, 116 were hospitalized and five people died. The causative agents in recreational waterborne disease are as varied as the exposure route; however, several trends are notable:1) the majority of outbreaks (61.5 percent; 48/78) were due to gastroenteritis following exposure to either infectious microbes or chemicals; 2) the majority of outbreaks (74.4 percent; 58/78) occured in treated water venues and 3) most were caused by the protozoa, Cryptospodium.

Cryptosporidium has been in the headlines before, causing the largest waterborne outbreak in modern US history in Milwaukee, Wisconsin in the 90s. In this outbreak, 50+ people died and 400,000 cases of iliness were reported. Resistant to chlorine disinfection, Cryptosporidium altered our focus for drinking water treatment to include uitraviolet light or filtration. A single outbreak of Cryptosporidium at a spray park in New York resulted in over 2,000 cases of illness, mostly among young children.

Other causative microbial agents of recreational waterborne disease from 2005-2006 include: Norovirus, Giardia, Naegleria, Leptospira, Vibrio spp., Campylobacter jejuni, Shigella sonnei, Pseudomonas aeruginosa and Legionella. Two outbreaks from exposure to excessive amounts of copper sulfate in a lake and liquid chlorine/muriatic acid in a swimming pool were also documented. For 12 outbreaks (15 percent) a causative agent could not be identified, although for most, a microbial pathogen was suspected. An understanding of etiologic agents involved in recreational waterborne disease is important for appropriate monitoring, intervention and control.

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