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Recreational Water Illness (RWI)

Underlying causes of Recreational Water Illness

Undetected Pool Dangers

A CDC report reveals a surge in recreational water illnesses due to chlorine-resistant pathogens and disinfection byproducts (DBPs). The chart shows a significant spike in outbreaks, particularly acute gastrointestinal illness (AGI), during the summer months of June through August in 2011-2012. This data highlights the urgent need for enhanced safety measures in public pools to protect against eye, skin, and respiratory illnesses. Safer water means healthier summers for our kids.

Recreation Water - associated Outbreaks, by Predominant Illness* and Month - United States, 2011 - 2012

Abbreviation/Terms: AGI: acute gastrointestinal illness; ARI: acute respiratory illness; Eye: illness, condition or symptom related to eyes; Multiple: a combination of predominant illnesses; Skin: illness, condition or symptom related to skin
* n=90; The category of illness reported by ≥50% of ill respondents.

Several children had to be hospitalized because of the outbreak.

Kids Hospitalized in Pool Outbreak

The CDC issued a new report on May 20, chronicling a recent bacteria outbreak from a swimming community pool. According to the report, the Pennsylvania Department of Health (PADOH) received multiple complaints of gastrointestinal illness on June 7, 2021, from patrons who had visited and swam at a community pool on May 31 that year. The agency identified 15 cases of E. coli infection among children ages 4 to 14, with nine confirmed cases and six probable cases.

"Some of the children who tested positive for E. coli also tested positive for C. difficile."

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Etiology of RWI

The interaction between chlorine and contaminants results in generation of
Disinfection Byproducts (DBPs)

Enzyme (saliva)

Accumulation of Contaminants & DBPs reduce Oxidation Potential (ORP)
Reduced ORP increases the time required for chlorine to kill bacteria (see biofilms).

Biofilm Evolution

  1. Low solubility organics (body oils, lotions etc.) adsorb onto the piping forming a barrier film.
  2. Reduced ORP allows bacteria to survive longer allowing adsorption & absorption.
  3. Barrier film provides a protective shelter from the chlorine in a warm and nutrient rich environment.
  4. Adaptive bacteria then form biofilms under which the bacteria thrive and propagate.
  5. Protected from the chlorine, encapsulated colonies are Chlorine Resistant.
  6. Literally hundreds of different species of bacteria can thrive within the biofilm.
  7. Detached bacteria (5) are returned to the pool where they are ingested, resulting in infection.
Evolution of biofilm
Biofilm in pipe

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Etiology treated water
Crypto Hatching

Cryptosporidium

  • Cryptosporidium is the leading cause of RWI.
  • Cryptosporidium is introduced into the pool water by someone infected by the parasite.
  • Cryptosporidium oocyst comprise a multi-layer membrane.
  • The sporozoites residing inside are highly protected - Chlorine Resistant.
  • Cryptosporidium can survive & infect bathers for over a week with typical chlorine concentrations. .