Swim at Your Own Risk

CDC warns improper swimming practices and pool cleaning can cause major waterborne bacteria illness.


Hotel pools and hot tubs are breeding grounds for waterborne bacteria—and they can be deadly. Between 2000 and 2014, germs spread through treated recreational water caused at least 27,219 illnesses and 8 deaths.

According to a CDC study, efforts to prevent outbreaks have had mixed results. The number of Legionella-related respiratory disease outbreaks increased over time, while Pseudomonas-related skin infection outbreaks declined and Cryptosporidium-related diarrheal disease outbreaks leveled off.

Legionella, which can cause severe pneumonia and flulike symptoms, was responsible for 16% of outbreaks. Another 13% was due to Pseudomonas, which can cause “hot tub rash” and swimmer’s ear. When a pool, hot tub, or water playground isn’t cleaned properly, bacteria grow and form “biofilm” on wet surfaces, ideal growing grounds for bacteria like Legionella and Pseudomonas. It’s harder for disinfectants to kill these bacteria when they are protected by biofilm, the CDC says.

The worst offender was Cryptosporidium, which caused 58% of the outbreaks and 89% of the illnesses. “Swallowing just a mouthful of water with Crypto in it can make otherwise healthy kids and adults sick for weeks,” said Michele Hlavsa, RN, MPH, chief of the CDC’s Healthy Swimming Program. Chlorine can’t kill Cryptosporidium quickly, she cautions. The best way to avoid it is to keep it out of the water in the first place. That means keeping anyone (usually young children) with stomach problems or diarrhea out of the pool.

Other CDC tips:

  • Check the inspection scores for pools, hot tubs, and water playgrounds.
  • Use a test strip from a pool supply store to check the pH and bromine or free chlorine levels.
  • Don’t swallow pool water.
  • Take kids on regular bathroom breaks; change diapers in the diaper-changing area, away from the water.

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