Epidemiology and Infection

Contaminated drinking water in one town manifesting as an outbreak of cryptosporidiosis in another

J. M. McANULTY a1a3c1, W. E. KEENE a1, D. LELAND a1, F. HOESLY a1, B. HINDS a2, G. STEVENS a2 and D. W. FLEMING a1
a1 Oregon Health Division, Center for Disease Prevention and Epidemiology, 800 NE Oregon Street, Portland, Oregon 97232
a2 Jackson County Health Department, 1005 E. Main Street, Medford, Oregon 97504
a3 Centers for Disease Control and Prevention, Division of Field Epidemiology, 1600 Clifton Road, NE Atlanta, Georgia 30333


In early 1992 we identified an outbreak of cryptosporidiosis in Oregon and sought to identify and control its source. We used a series of studies to identify risk factors for illness : (i) a case-control study among employees of a long-term-care facility (LTCF); (ii) a matched case-control study of the general community; (iii) a cohort study of wedding attendees; and (iv) a cross-sectional survey of the general community. Drinking Talent water was associated with illness in the LTCF (OR = 22·7, 95% CI = 2·7–1009·0), and in the community (matched OR = 9·5, 95% CI 2·3–84·1). Drinking Talent water was associated with illness only among non-Talent residents who attended the wedding (P < 0·001) and in the community (RR = 6·5, 95% CI 3·3–12·9). The outbreak was caused by contaminated municipal water from Talent in the absence of a discernible outbreak among Talent residents, suggesting persons exposed to contaminated water may develop immunity to cryptosporidiosis.

(Accepted March 24 2000)

c1 Author for correspondence: Communicable Diseases Surveillance and Control Unit, New South Wales Health Department, Locked Mail Bag 961, North Sydney, New South Wales, Australia.