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Volume 12, Number 4—April 2006

Research

Reducing Legionella Colonization of Water Systems with Monochloramine

Brendan Flannery*Comments to Author , Lisa B. Gelling†, Duc J. Vugia‡, June M. Weintraub§, James J. Salerno¶, Michael J. Conroy¶, Valerie A. Stevens*, Charles E. Rose*, Matthew R. Moore*, Barry S. Fields*, and Richard E. Besser*
Author affiliations: *Centers for Disease Control and Prevention, Atlanta, Georgia, USA; †California Emerging Infections Program, Oakland, California, USA; ‡California Department of Health Services, Richmond, California, USA; §City and County of San Francisco Department of Public Health, San Francisco, California, USA; ¶San Francisco Public Utilities Commission, Burlingame, California, USA

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Table 3

Factors associated with Legionella colonization of water heaters in sampled buildings, San Francisco, California

Factor No. samples % Legionella colonization Adjusted prevalence ratio (95% CI)* p value
Residual disinfectant
Chlorine 157 29 Referent
Chloramine 159 1 0.04 (0.01–0.21) <0.001
Water heater temperature, °C
<30 29 21 Referent
30–39 68 24 0.43 (0.27–0.70) 0.001
40–49 131 18 0.27 (0.16–0.46) 0.001
>50 88 1 0.09 (0.05–0.18) 0.001
Building height (stories)
3–10 215 11 Referent
>10 101 24 2.96 (1.51–5.79) 0.002
Disruption in service in last 3 mo
Yes 39 26 2.26 (1.31–3.88) 0.003
No 277 13 Referent

*Prevalence ratios and 95% confidence intervals (CIs) were adjusted for repeated sampling and for effects of all other variables.

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