Epidemiology and Infection

Cambridge Journals Online - CUP Full-Text Page
Epidemiology and Infection (2010), 138:491-500 Cambridge University Press
Copyright © Cambridge University Press 2009

Original Papers


Outbreak of giardiasis associated with a community drinking-water source

E. R. DALYa1 c1, S. J. ROYa2, D. D. BLANEYa1a3, J. S. MANNINGa1, V. R. HILLa3, L. XIAOa3 and J. W. STULLa1a4

a1 New Hampshire Department of Health and Human Services, Concord, NH, USA
a2 New Hampshire Department of Environmental Services, Concord, NH, USA
a3 Centers for Disease Control and Prevention, Atlanta, GA, USA
a4 University of New Hampshire, Durham, NH, USA
Article author query
daly er [PubMed]  [Google Scholar]
roy sj [PubMed]  [Google Scholar]
blaney dd [PubMed]  [Google Scholar]
manning js [PubMed]  [Google Scholar]
hill vr [PubMed]  [Google Scholar]
xiao l [PubMed]  [Google Scholar]
stull jw [PubMed]  [Google Scholar]


Giardiasis is a common waterborne gastrointestinal illness. In 2007, a community giardiasis outbreak occurred in New Hampshire, USA. We conducted a cohort study to identify risk factors for giardiasis, and stool and environmental samples were analysed. Consuming tap water was significantly associated with illness (risk ratio 4·7, 95% confidence interval 1·5–14·4). Drinking-water samples were coliform-contaminated and a suspect Giardia cyst was identified in a home water filter. One well was coliform-contaminated, and testing indicated that it was potentially under the influence of surface water. The well was located 12·5 m from a Giardia-contaminated brook, although the genotype differed from clinical specimens. Local water regulations require well placement at least 15 m from surface water. This outbreak, which caused illness in 31 persons, represents the largest community drinking-water-associated giardiasis outbreak in the USA in 10 years. Adherence to well placement regulations might have prevented this outbreak.

(Accepted August 11 2009)

(Online publication September 15 2009)

Key Words:Drinking water; Giardia; groundwater; outbreak


c1 Author for correspondence: E. R. Daly, MPH, Communicable Disease Surveillance Section, New Hampshire Department of Health and Human Services, 29 Hazen Drive, Concord, NH 03301-6504, USA. (Email: erdaly@dhhs.state.nh.us)