Treated Recreational Water—Associated Outbreaks of Cryptosporidiosis

CAPT Charles Otto

Michele C. Hlavsa


The annual number of nationally reported cryptosporidiosis outbreaks associated with treated recreational water venues (e.g., pools, water parks, and interactive fountains) has increased substantially since 2004: seven reported treated recreational water–associated outbreaks in 2004, 19 in 2006, and, provisionally 26 in 2007 (as of December 22, 2008). Cryptosporidium's ability to cause communitywide outbreaks, such as the 2007 statewide cryptosporidiosis outbreak in Utah, underscores the need for rapid implementation of control measures once an increase in case reporting is noted rather than waiting for an outbreak investigation to implicate a specific transmission source. Such a response is outlined in the Cryptosporidiosis Outbreak Response & Evaluation (CORE) recommendations (, which call for preoutbreak adoption of a disease action threshold and rapid mobilization of community partners (e.g., operators of pools and child care centers) to implement control measures once it is exceeded.


Cryptosporidium's ability to cause communitywide outbreaks also highlights the need for a uniform national set of aquatic standards governing the design, construction, operation, and maintenance of treated recreational water venues. In the United States, pool codes are reviewed and approved by individual state or local public health officials. Thus, code requirements for addressing issues like preventing and responding to recreational water– associated outbreaks can vary substantially among states and communities. In 2007, in response to a national recreational water illness prevention workshop, CDC initiated an effort to develop a national Model Aquatic Health Code, or MAHC (, which will address healthy swimming issues like cryptosporidiosis. The overriding objectives of this effort are to 1) develop a knowledgebased and scientifically supported health code that reduces risk and promotes healthy recreational water experiences and 2) make the best standards available for voluntary adoption by state and local agencies seeking to update their pool codes. It follows that this would allow state and local agencies to optimize their ability to promote healthy swimming and simultaneously save the time of valuable human resources. The increased incidence of treated recreational water–associated outbreaks of cryptosporidiosis underscores the need for proactive steps such as those outlined in the CORE and moving forward in developing the MAHC.