Cryptosporidium Disease Outbreaks in US Public Pools Are Increasing Says CDC

There’s a disease called Cryptosporidium that’s been spreading over the past few years, and the CDC is asking everyone to help stop it from spreading. The CDC asks everyone to just stop peeing and pooping in pools and hot tubs!

The U.S. Centers for Disease Control and Prevention documented 90 Cryptosporidium disease outbreaks. The recent study of the disease is related to the chlorine-resistant parasite observed in public water venues between 2011 and 2012, the agency said in a new report.

Here is part of CDC’s report:

Cryptosporidium continues to be the dominant etiology of recreational water–associated outbreaks. Half of all treated recreational water–associated outbreaks reported for 2011–2012 were caused by Cryptosporidium. Among treated recreational water–associated outbreaks of gastrointestinal illness that began in June–August, >90% were caused by Cryptosporidium, an extremely chlorine-tolerant parasite that can survive in water at CDC-recommended chlorine levels (1–3 mg/L) and pH (7.2–7.8) for >10 days (4). In contrast, among 14 untreated recreational water–associated outbreaks of gastrointestinal illness starting in June–August, 7% (one) were caused by Cryptosporidium. The decreased diversity of infectious etiologies causing treated recreational water–associated outbreaks is likely a consequence of the aquatic sector’s reliance on halogen disinfection (e.g., chlorine or bromine) and maintenance of proper pH, which are well documented to inactivate most infectious pathogens within minutes (5). Continued reporting of treated recreational water–associated outbreaks caused by chlorine-intolerant pathogens (e.g., E. coli O157:H7 and norovirus) highlights the need for continued vigilance in maintaining water quality (i.e., disinfectant level and pH), as has been recommended for decades (5).

In the United States, codes regulating public treated recreational water venues are independently written and enforced by individual state or local agencies; the consequent variation in the codes is a potential barrier to preventing and controlling outbreaks associated with these venues. In August 2014, CDC released the first edition of MAHC (, a comprehensive set of science-based and best-practice recommendations to reduce risk for illness and injury at public, treated recreational water venues. MAHC represents the culmination of a 7-year, multi-stakeholder effort and is an evolving resource that addresses emerging public health threats, such as treated recreational water-associated outbreaks of cryptosporidiosis, by incorporating the latest scientifically validated technologies that inactivate or remove infectious pathogens. For example, MAHC recommends additional water treatment (e.g., ultraviolet light or ozone) to inactivate Cryptosporidium oocysts at venues where WBDOSS data indicate there is increased risk for transmission. MAHC recommendations can be voluntarily adopted, in part or as a whole, by state and local jurisdictions.

The number of reported untreated recreational water–associated outbreaks confirmed or suspected to be caused by cyanobacterial toxins has decreased, from 11 (2009–2010) to one (2011–2012) (6). This decrease is likely the result of a decrease in outbreak reporting rather than a true decrease in incidence. CDC is currently developing a mechanism for reporting algal bloom–associated individual cases through NORS to better characterize their epidemiology.

The findings in this report are subject to at least two limitations. First, the outbreak counts presented are likely an underestimate of actual incidence. Many factors can present barriers to the detection, investigation, and reporting of outbreaks: 1) mild illness; 2) small outbreak size; 3) long incubation periods; 4) wide geographic dispersion of ill swimmers; 5) transient nature of contamination; 6) setting or venue of outbreak exposure (e.g., residential backyard pool); and 7) potential lack of communication between those who respond to outbreaks of chemical etiology (e.g., hazardous materials personnel) and those who usually report outbreaks (e.g., infectious disease epidemiologists). Second, because of variation in public health capacity and reporting requirements across jurisdictions, those reporting outbreaks most frequently might not be those in which outbreaks most frequently occur.