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CDC Reports on Giardiasis and Cryptosporidiosis Occurrence

The Centers for Disease Control and Prevention (CDC) have released “Surveillance Summaries” documenting the occurrence of Giardiasis and Cryptosporidiosis in the U.S. for the period of 2009-2010. You can download the Surveillance Summaries for more detail about the occurrence of both of these diseases. These pathogens have had a significant influence on the regulation of both surface water and ground water sources of drinking water over the past few years.

In 2009, 7,656 confirmed and probable cases of cryptosporidiosis were reported, with 8,951 cases reported for 2010. Cases were most frequently reported in children aged 1–9 years, followed by adults aged 25–29 years. Cryptosporidiosis is most often associated with increased use of treated recreational water venues (pools, etc.) during the summer, particularly among younger children. Cryptosporidium has become the leading cause of reported treated recreational water–associated outbreaks of gastroenteritis. CDC notes that, since the adoption and implementation of stricter EPA regulations for surface water treatment at community water systems, this source of Cryptosporidium has essentially been eliminated as a source of cryptosporidiosis.

During 2009–2010, the total number of reported cases of giardiasis increased slightly from 19,403 for 2009 to 19,888 for 2010. Drinking water is an important vehicle for Giardia transmission. G. intestinalis was the single most frequently identified pathogen in all drinking water outbreaks reported in the United States during 1971–2006, responsible for 28% of outbreaks with an identified etiology. Untreated drinking water was identified as a risk factor for sporadic giardiasis in studies in the United States and New Zealand. Untreated groundwater appeared to be particularly risky if it was acquired from poorly constructed or maintained wells that might have been subject to surface water contamination. Treated or untreated recreational water also has been implicated as a vehicle of giardiasis transmission. Although giardiasis is the most common enteric parasitic infection in the United States, knowledge of its epidemiology is still lacking. The majority of data on giardiasis transmission comes from outbreak investigations; however, during 2009–2010, <1% of reported giardiasis cases were associated with outbreaks.