Recreational Water Systems

Pathogens and chemicals found in various recreational waters that we swim in can cause recreation al water–associated illnesses (RWIs). Chemicals used for treating recreational water can cause illness or injury through direct contact or by inhalation. RWIs can be gastrointestinal, respiratory, neurologic, skin (i.e., wound infection), ear, and eye illness. The most frequently reported illness for RWI outbreaks is diarrhea, which is most commonly caused by Cryptosporidium pdf icon[PDF – 1 page], followed by Giardia pdf icon[PDF – 1 page], Shigella, and norovirus.

Treated Recreational Water (Swimming Pools, Waterparks, Water Playgrounds, Hot tubs/Spas)

  • Description – Outbreaks associated with exposure to treated recreational water can be caused by pathogens or chemicals in venues such as pools, hot tubs/spas, and water playgrounds. The most frequently reported illness for treated recreational water–associated outbreak is diarrhea. Swallowing even a small amount of water contaminated with enteric pathogens can make swimmers sick.
  • Detection – An outbreak associated with recreational water is the occurrence of similar illnesses in two or more persons, epidemiologically linked by location and time of exposure to recreational water or to pathogens or chemicals aerosolized or volatilized from recreational water into the surrounding air. Public health officials might be alerted to an outbreak when they see an increase in the number of case reports. Typically, these reports come from diagnostic laboratories or healthcare providers. Additionally, public health officials might receive inquiries from healthcare providers or the public regarding illness in a specific group of people.
  • Investigation – Working with an environmental health practitioner can aide in identifying what issues related to the operation and management of public treated recreational water venues contributed to the outbreak. Outbreaks caused by chlorine-susceptible pathogens signal the need to ensure that the water is adequately halogenated (chlorinated or brominated). Outbreaks caused by the extremely chlorine tolerant pathogen Cryptosporidium do not necessarily signal issues in operations.
  • Control – Chlorine (or bromine) concentration and pH should be tested and recorded to ensure that most pathogens are properly inactivated. Chlorine will inactivate most pathogens that cause RWIs within minutes. However, Cryptosporidium can survive for more than 7 days in adequately treated recreational water.

Hot Tubs/Spas

  • Description – “Hot tub rash“, a skin infection caused by Pseudomonas, is a common RWI spread through improperly operated hot tubs/spas. Legionella can cause Legionnaires’ disease, a severe type of pneumonia, and Pontiac fever, a milder illness than Legionnaires’ disease without pneumonia, are also commonly associated with improperly operated hot tubs/spas. High water temperatures and aerosolization of water pose a challenge for maintaining the disinfectant concentration. When disinfection concentration decreases, bacteria can amplify in hot tub/spa water.
  • Detection – An outbreak associated with recreational water is the occurrence of similar illnesses in two or more persons, epidemiologically linked by location and time of exposure to recreational water or to pathogens or chemicals aerosolized or volatilized from recreational water into the surrounding air. Public health officials might be alerted to an outbreak when they see an increase in the number of case reports. Typically, these reports come from diagnostic laboratories or healthcare providers. Additionally, public health officials might receive inquiries from healthcare providers or the public regarding illness in a specific group of people.
  • Investigation – Working with an environmental health practitioner can aide in identifying what issues related to the operation and management of public treated recreational water venues contributed to the outbreak. Outbreaks caused by chlorine-susceptible pathogens signal the need to ensure that water is adequately halogenated (chlorinated or brominated). Outbreaks caused by the extremely chlorine tolerant pathogen Cryptosporidium do not necessarily signal issues in operations.
  • Control – Drain all water from the hot tub/spa. Vigorously scrub all hot tub/spa surfaces, skimming devices, and circulation components. Replace filters (for cartridge or diatomaceous earth filters) or filter media (for sand filters).

Oceans, Lakes, and Rivers (Untreated Water)

  • Description – Oceans, lakes, and rivers can be contaminated with pathogens from sewage spills, animal waste, water runoff following heavy rain, fecal incidents, and naturally occurring organisms. Illnesses associated with ocean, lake, and river exposure can vary based on the type of pathogen and can affect the gastrointestinal tract (diarrhea, vomiting), ears, eyes, skin, or central nervous system. Harmful algal blooms (HABs) are visible colonies of cyanobacteria and microalgae. Contributors to the formation of HABs include nutrient pollution and warm water. Some HABs can create toxins that cause illness in people or animals through direct contact, ingestion, or inhalation. Cyanobacteria are usually found in fresh water but have occasionally caused coastal blooms—sometimes severe.
  • Detection – An outbreak associated with recreational water is the occurrence of similar illnesses in two or more persons, epidemiologically linked by location and time of exposure to recreational water or to pathogens or chemicals aerosolized or volatilized from recreational water into the surrounding air.
  • Investigation – Investigations of outbreaks associated with untreated recreational water can be supported environmental investigations (including but not limited to beach monitoring data and sanitary surveys) to provide information about potential sources of contamination (e.g., sewage spills, nutrient pollution). Pathogens introduced by environmental contamination or ill swimmers might not be killed or removed as readily as in treated venues due to the lack of disinfection and filtration.
  • Control – Control measures might consider water quality from beach monitoring activities. Beach closures or other restrictions on use (e.g., no swimming, no fishing) may be implemented by water body managers until water quality concerns are eliminated. Control measures may also consider factors that would improve water quality (e.g., by reducing the influx of environmental contaminants, improving the circulation of stagnant water). Monitoring requirements for untreated recreational water venues vary by jurisdiction.
Additional Resources