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Appendix A

Glossary of Definitions

aquatic facility-related health events not associated with recreational water Chemical injury cases and outbreaks (e.g., mixing of pool chemicals that release toxic gas) at aquatic facilities in which exposure to water was not the cause of illness. Although these events are not classified or analyzed as waterborne-disease outbreaks, they highlight important public health and safety concerns related to the design, operation, and maintenance of recreational water venues.
backwash Flow of water through filter element(s) or media in a reverse direction to dislodge accumulated dirt, debris, and/or filter aid, and remove them from the filter tank.
backwash cycle Time required to thoroughly backwash the filter system.
bather load The number of bathers using a swimming pool or spa at any one time. The maximum bather load is usually determined by a state or local pool code, based on surface area and depth of the pool or spa.
biofilm Microbial cells that adhere to a surface through a matrix of primarily polysaccharide materials in which they are encapsulated. These can grow on piping and surfaces of aquatic venues and can be notoriously difficult to remove. They offer protection to microbes from disinfectants (e.g., chlorine) in the water.
cercarial dermatitis Dermatitis caused by contact with or direct invasion through the skin or a break in the skin by the cercariae (larval stage) of certain species of schistosomes, a type of parasite, for which the normal hosts are birds and nonhuman mammals. Dermatitis is an allergic response to contact with cercariae and does not lead to parasitic infestation in humans and produces no long-term disease.
class Waterborne disease and outbreaks are classified according to the strength of the epidemiologic and laboratory data implicating recreational water as the source of the disease or outbreak (see Table 1).
chloramines A group of disinfection by-products or weak disinfectants formed when free chlorine combines with nitrogen-containing compounds in the water (e.g., urine or perspiration). Tri- and di-chloramine can cause eye, skin, lung, and throat irritation and can accumulate in the water and air surrounding treated recreational water venues. In drinking water treatment, monochloramine is used for disinfection to reduce formation of disinfection by-products created when using chlorine as a disinfectant (see combined chlorine level).
coliforms All aerobic and facultative anaerobic, gram-negative, nonspore-forming, rod-shaped bacteria that ferment lactose with gas formation within 48 hours at 95ºF (35ºC).
combined chlorine level See chloramines. Chlorine that has combined with organic compounds in the water and is no longer an effective disinfectant for recreational water. This value is derived by subtracting the free chlorine test level from total chlorine test level. The combined chlorine level is likely to include combined compounds in addition to chloramines.
contact time The length of time water (and pathogens) is exposed to a disinfectant, usually measured in minutes (e.g., chlorine contact time).
Cryptosporidium The taxonomy of Cryptosporidium has evolved as a result of advancements in molecular methodology and genotyping. The former C. parvum now refers to a species that is zoonotic and infects ruminants and humans. C. hominis refers to the species of Cryptosporidium that infects only humans, primates, and monkeys. Both species were referred to previously as C. parvum.
dermatitis Inflammation of the skin. In this Surveillance Summary, the term dermatitis is used to denote a broad category of skin-related symptoms (e.g., folliculitis, cellulitis, burns, or rash).
disinfection by-products Chemicals formed in water through reactions between organic matter and disinfectants. Includes chloramines, also known as combined chlorines.
etiologic agent The pathogen, chemical, or toxin causing a waterborne disease or outbreak. Infectious etiologic agents include bacteria, parasites, and viruses.
fecal coliforms Coliforms that grow and ferment lactose to produce gas at 112.1ºF (44.5ºC) within 24 hours.
fill-and-drain pools Small pools, often constructed of plastic, which might be inflatable, and filled with tap water without any ongoing chemical disinfection or filtration. Sometimes called kiddie pools.
filtration The process of removing suspended particles from water by passing it through one or more permeable membranes or media of limited pore diameter (e.g., sand, anthracite, or diatomaceous earth).
folliculitis Inflammation of hair follicles. Spa-associated folliculitis is usually associated with infection by Pseudomonas aeruginosa.
free chlorine The chlorine in water not combined with other constituents; therefore, it is able to serve as an effective disinfectant (also referred to as free available chlorine or residual chlorine). Measuring the free chlorine level is a common water-quality test.
freshwater (untreated water) Surface water (e.g., water from lakes, rivers, or ponds) that has not been treated in any way to enhance its safety for recreational use.
interactive fountain A fountain or water spray device intended for (or accessible to) recreational use. They usually do not have standing water as part of the design. These are sometimes called spray pads, splash pads, wet decks, or spray grounds. In contrast, noninteractive (ornamental) fountains intended for public display rather than recreational use are often located in front of buildings and monuments, and their water is not easily accessible for public use.
marine water Untreated recreational water at an ocean or estuarine setting.
microcystin toxin A secondary metabolite of blue-green algae (cyanobacteria) that can have toxic effects on humans and animals, potentially causing a wide range of illness or even death when exposure to accumulated toxins in fresh or marine water occurs.
mixed agent outbreak More than one type of etiologic agent is identified in clinical specimens from affected persons, and each etiologic agent is found in >5% of positive clinical specimens (e.g., an outbreak with Giardia spp. [parasites] and Salmonella spp. [bacteria], with each agent identified in >5% of stool specimens).
oocyst The infectious stage of Cryptosporidium species and certain other coccidian parasites with a protective wall that facilitates survival in water and other environments and renders the parasite extremely resistant to chlorine.
predominant illness The type of illness most commonly expressed in a substantial proportion (>50%) of patients (e.g., gastroenteritis, dermatitis, and acute respiratory illness). When more than one illness type seems to define the character of the waterborne disease and outbreak, they are listed together as predominant illnesses.
recreational water venue A body of water used for the purpose of recreation (e.g., swimming, soaking, or athletics), including any structure that encloses this water. It can include lakes and ponds, rivers, springs, the ocean, and man-made venues (e.g., swimming pools, spas, and water parks) that do not necessarily include standing water (e.g., interactive fountains).
reservoir, impoundment An artificially maintained lake or other body of water created for the collection and storage of water. This body of water might be available for recreational use.
setting Location where exposure to contaminated water occurred (e.g., swimming beach, water park, and hotel).
spa Any structure, basin, chamber, or tank (located either indoors or outdoors) containing a body of water intended to be used for recreational or therapeutic purposes that usually contains a waterjet or aeration system. It is operated at high temperatures and is usually not drained, cleaned, or refilled after each use. It sometimes is referred to as a hot tub or whirlpool.
spray park A recreational water venue solely consisting of multiple interactive fountains.
total chlorine A common water-quality test that measures the chlorine in water that is free for disinfection (free chlorine) plus that combined with other organic materials (combined chlorine). The combined chlorine level is derived by subtracting the free chlorine test result from the total chlorine test result.
total coliforms Nonfecal and fecal coliforms that are detected by using a standard test.
treated water Water that has undergone a disinfection or treatment process (e.g., chlorination and filtration) for the purpose of making it safe for recreation. Typically, this refers to any recreational water in an enclosed, manufactured structure but might include swimming or wading pools, fountains, or spas filled with treated tap water (e.g., small wading kiddie pool) or untreated water (e.g., mineral spring water) that receives no further treatment.
turbidity A measurement of suspended particulate matter in water expressed as nephelometric turbidity units (NTU).
turnover rate The time required to theoretically recirculate the entire volume of water in a swimming pool, spa, or hot tub.
ultraviolet light The segment of the light spectrum between 100-300 nanometers (nm).
ultraviolet light disinfection unit A device that produces ultraviolet light between 250-280 nm for the purpose of inactivation of microorganisms by UV radiation.
untreated water Surface water that has not been treated or disinfected in any way (i.e., lakes, rivers, oceans, and reservoirs).
user Any person using a pool, spa, or hot tub and adjoining deck area.
Vibrio species A genus of comma-shaped, gram-negative Proteobacteria that include various human pathogens. Certain species are found in salty or brackish water and can cause illness by contamination of a wound or epithelial site (e.g., eardrums or sinus cavities). Sequelae can include sepsis and death.
waterborne-disease outbreak Water exposure in which two or more persons have been epidemiologically linked to recreational water by location of exposure, time, and illness.
waterborne disease and outbreak surveillance system (WBDOSS) The surveillance system that contains the outbreaks and case reports reported by jurisdictional public health authorities. Inputs into this system are illustrated in Figure 1.
WBDOSS Surveillance Summary The biennial summaries of waterborne-disease outbreaks and cases associated with recreational water, drinking water and water not intended for drinking are published in the MMWR. These publications also discuss waterborne-disease data from other surveillance systems (e.g., Vibrio) and disseminate waterborne-disease prevention messages.
water-quality indicator A microbial, chemical, or physical parameter that indicates the potential risk for infectious diseases associated with using the water for drinking, bathing, or recreational purposes. The best indicator is one with a density or concentration that correlates best with health effects associated with a type of hazard or pollution (e.g., turbidity, coliforms, fecal coliforms, Escherichia coli, enterococci, free chlorine level).

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Date last reviewed: 9/4/2008


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