Medical Professionals

Nurse Speaking to a Mother and Child

The number of recreational water illness (RWI) outbreaks reported annually has increased dramatically in recent years. Cryptosporidium, which can stay alive for days even in well-maintained pools, has become the leading cause of swimming pool–related outbreaks of diarrheal illness. From 2015 through 2019, public health officials from 36 states and the District of Columbia reported a total of 208 outbreaks associated with treated recreational water. Cryptosporidium caused 76 of these outbreaks, resulting in 2,492 cases of illness.1

Studies show that the swimming public believes that chlorine instantly kills all pathogens. These data also show that swimmers don’t think about swimming as a shared water experience. Unfortunately, these misconceptions lead to risky behaviors, such as swimming during diarrheal illness and swallowing recreational water, which lead to transmission of pathogens that cause RWIs. It is important for medical professionals to educate their patients and dispel misconceptions that lead to illness.2

Five Prevention Messages

Here are five simple prevention messages medical professionals can share with their patients to help them proactively protect their health and the health of others every time they swim.

  • Don’t swim while ill with diarrhea.
  • For patients with cryptosporidiosis, don’t swim for an additional 2 weeks after diarrhea has resolved.
  • Don’t swallow the water while swimming.
  • Keep ears as dry as possible and dry ears thoroughly after swimming.
  • Don’t swim when you have open wounds.
Training and Patient Education
Infection Control

Infection control practitioners need to know the recommendations developed by CDC and the Healthcare Infection Control Practices Advisory Committee for hydrotherapy tanks.

The following resources are also available within the CDC Healthy Swimming website:


  1. Hlavsa MC, Aluko SK, Miller AD, et al. Outbreaks Associated with Treated Recreational Water — United States, 2015–2019. MMWR Morb Mortal Wkly Rep 2021;70:733–738.
  2. Castor ML, Beach MJ. Reducing illness transmission from disinfected recreational water venues: Swimming, diarrhea, and the emergence of a new public health concern. Pediatr Infect Dis J. 2004;23(9):866–70.
Page last reviewed: February 18, 2022