Hoping to address the growing threat of cryptosporidium, the Centers for Disease Control and Prevention has released revised guidelines for diarrheal fecal accident response.

The new guidelines the first in seven years reflect recent research findings indicating that it takes longer to inactivate crypto than previously thought, according to CDC officials.

This means that to inactivate 99.9 percent of crypto oocysts, in the event of a diarrheal contamination, operators should raise the free chlorine concentration to 20 ppm and maintain the water?s pH between 7.2 and 7.5, and temperature at approximately 77 degrees Fahrenheit. These levels should be sustained for a minimum of 12.75 hours. Previous recommendations called for 20 ppm for eight hours.

This change means longer facility closures, but it?s important in preventing crypto outbreaks. ?We are seeing an increase in the number of crypto outbreaks,? says Michele Hlavsa, epidemiologist with CDC. ?The new guidelines will better ensure that pool water will be fully disinfected.?

In 2007, officials documented some of the worst crypto outbreaks to date. Several states saw unusually large outbreaks, including Idaho, South Dakota, Pennsylvania and Utah, which recorded more than 1,900 cases. Crypto is spread by swallowing pool water that?s been contaminated with feces, usually diarrhea.

To that end, Hlavsa said the revisions focused on the diarrheal response. Formed stool is not as likely to pose a risk because it typically does not contain pathogens. Pathogens also are more likely to be contained within the stool. Guidelines for formed stool response remain largely unchanged.

The new guidelines will be incorporated into the Model Aquatic Health Code, which is currently in development. They are available now on the CDC Web site www.cdc.gov/healthyswimming/fecal_response.htm. The corresponding research will be published in an upcoming volume of the Journal of Water and Health