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Outbreak of giardiasis associated with a community drinking-water source

  • E. R. DALY (a1), S. J. ROY (a2), D. D. BLANEY (a1) (a3), J. S. MANNING (a1), V. R. HILL (a3), L. XIAO (a3) and J. W. STULL (a1) (a4)...

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.

Corresponding author
*Author for correspondence: E. R. Daly, MPH, Communicable Disease Surveillance Section, New Hampshire Department of Health and Human Services, 29 Hazen Drive, Concord, NH03301-6504, USA. (Email:
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Epidemiology & Infection
  • ISSN: 0950-2688
  • EISSN: 1469-4409
  • URL: /core/journals/epidemiology-and-infection
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