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Notice to Readers: Revised Recommendations for Responding to Fecal Accidents in Disinfected Swimming Venues

The 2001 CDC recommendations (1) for responding to fecal accidents in disinfected swimming venues (e.g., swimming pools) have been revised. Recommendations for responding to diarrheal fecal accidents, which are thought to represent a higher infectious-disease transmission risk than formed-stool accidents, are based on the potential presence of the chlorine-resistant parasitic protozoa of the genus Cryptosporidium. New data indicate that the recommended CT inactivation value (or contact time)* is higher than previously published (2), when inactivation is measured at a higher pH using an outbreak-associated Cryptosporidium isolate (3). Based on these data, the CT inactivation value used in CDC fecal accident recommendations for 99.9% inactivation of Cryptosporidium has been changed from 9,600 mg-min/L to 15,300 mg-min/L. This change translates into longer swimming pool closures to ensure inactivation of Cryptosporidium.

Swimming pool operators should check existing guidelines from local or state regulatory agencies before using these recommendations, because CDC recommendations do not replace existing state or local regulations or guidelines. The CDC revised fecal accident response recommendations are available at


  1. CDC. Responding to fecal accidents in disinfected swimming venues. MMWR 2001;50:416--7.
  2. Korich DG, Mead JR, Madore MS, Sinclair NA, Sterling CR. Effects of ozone, chlorine dioxide, chlorine, and monochloramine on Cryptosporidium parvum oocyst viability. Appl Environ Microbiol 1990;56:1423--8.
  3. Shields JM, Arrowood MJ, Hill VR, Beach MJ. Inactivation of Cryptosporidium parvum under chlorinated recreational water conditions. J Water Health 2008. In Press.

* The CT number refers to the concentration (C) of free chlorine in milligrams per liter (parts per million) multiplied by time (T) in minutes at a specific pH and temperature.

At pH 7.2--7.5, 77°F (25°C).

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Date last reviewed: 2/14/2008


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Morbidity and Mortality Weekly Report
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