June 17, 2024

CDC Tracks Cryptosporidium and Legionnaires Disease Outbreaks Traced to Treated Recreational Water

Cryptosporidium and Legionnaires’ Disease outbreaks associated with treated creational water during 2000 to 2014 are traced by the Centers for Disease Control and Prevention in their weekly Morbidity and Mortality Report for the week of May 18, 2018. During that time frame, 493 outbreaks caused at least 27,219 illnesses and eight deaths.

Cryptosporidium and Legionella Outbreaks at Public Pools and Water Parks

Public health officials, owners of these parks, bathers, and parents of young children can help minimize the risk for these outbreaks. Cryptosporidium outbreaks increased 25% by year during the 2000 – 2006 seasons, but no significant trend occurred after 2007.

These outbreaks are caused by both pathogens and chemicals in venues such as pools, hot tubs and spas, and interactive water play features. Among the 363 outbreaks with a confirmed infectious source, 212 were caused by Cryptosporidium (which causes gastrointestinal illness), 57 by Legionella (which causes Legionnaires Disease, a severe kind of pneumonia), and 47 by Pseudomonas (which causes hot tub rash and swimmer’s ear). Six of the eight reported deaths occurred in people who contracted Legionella.

Hotels were associated with 157, or 32%, of the 493 outbreaks. About half of the outbreaks started in the months of June, July, and August; another peak occurred in March. An outbreak is defined as similar illnesses in two or more persons, which are epidemiologically linked by location and time of exposure to recreational water, or to the pathogens or chemicals that are aerosolized into the surrounding air. The 275 outbreaks that started during the summer months were mostly caused by Cryptosporidium.

Treatment with chlorine is the primary barrier to the transmission of these pathogens. The CDC recommends concentrations of at least 1 part per million, when free available chlorine inactivates most pathogens within minutes. But, Cryptosporidium, which is extremely chlorine-tolerant, can survive for more than 7 days at that concentration.

Cryptosporidium is transmitted when a diarrheal incident occurs in the water and the contaminated water is swallowed. Legionella and Pseudomonas are effectively controlled by halogens (chlorine and bromine) in well-maintained treated water.

But, those pathogens can persist in a biofilm, which protects the bacteria and can increase when disinfectant concentrations aren’t constant. And about 20% of 13,864 routine inspections of public hot tubs and spas conducted in 2013 found improper disinfectant concentrations.

If a diarrheal incident occurs, the CDC recommends hyperchlorination to achieve Cryptosporidium inactivation. UV light or ozone systems can be added, especially when children under the age of 5 use the facility.

The public also needs to be educated. The key message to the public, especially parents of young children, is “Don’t swim or let your kids swim if sick with diarrhea.” People susceptible to Legionella, which includes the elderly and anyone with lung issues, should purchase test strips to measure bromine or free chlorine level and pH levels before they get into the water.

In addition, everyone should shower before they go into a public pool, spa, or water park, since that can rinse off perspiration, body oils, and traces of urine and fecal matter on the body. According to Water and Health.org, the strong smell in swimming pools is not chlorine, but from irritants produced when chlorine reacts with impurities. Showering before swimming to remove possible fecal matter and impurities also leaves the chlorine free to do its job: destroy pathogens.


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