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
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
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
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
corresponding research will be published in an upcoming
volume of the Journal of Water and Health