Abstract
Giardiasis Surveillance—United States, 2006–2008
Giardia intestinalis is the most common parasite seen in the United States. It is a reportable disease in all states except Indiana, Kentucky, Mississippi, North Carolina, and Texas. Reports of both suspected cases and laboratory confirmed cases were collected by the Centers for Disease Control and summarized in this report. Direct fluorescence assay is the gold standard for confirmation. In this report, approximately 20 000 cases were identified annually between 2006 and 2008. A bimodal distribution among age groups showed peaks in 1 to 9 year olds and 35 to 44 year olds. More cases were reported in northern states, though no statistical comparison was done. Twice as many cases were reported at the beginning of the summer, in June and July, and the authors postulated that this was due to increased swimming by children. They reasoned that, while restaurant outbreaks do occur, they are not common, and that this disease can be transmitted in chlorinated pools due to its highly infectious characteristics. Giardia only requires 10 cysts to initiate an infection and over 1 billion are found in single stool samples. In addition, pools are sometimes inadequately chlorinated, allowing increased survival of cysts.
(MMWR Surveill Summ. 2010; 59:15–28) JS Yoder, C Harral, MJ Beach.
Prepared by Anil Menon, MD, UTMB/NASA Aerospace Medicine Fellow, Galveston, TX, USA