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Reducing Legionella colonization in water systems with monochloramine.
Brendan Flannery1, Lisa B Gelling, Duc J Vugia
1Division of Bacterial and Mycotic Diseases, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia 30333, USA. bif4@cdc.gov
Emerging Infectious Diseases
|May 18, 2006
Summary
Switching municipal water disinfection from chlorine to monochloramine significantly reduced Legionella bacteria in hot water systems. This change may lower the risk of Legionnaires' disease outbreaks.
Area of Science:
- Environmental Science
- Public Health
- Microbiology
Background:
- Monochloramine disinfection of public water is linked to a lower risk of Legionnaires' disease.
- Legionella bacteria thrive in hot water systems, posing a significant public health risk.
Purpose of the Study:
- To assess the impact of switching from chlorine to monochloramine for water disinfection on Legionella colonization in building hot water systems.
- To evaluate the effectiveness of monochloramine in reducing Legionella presence in diverse building types.
Main Methods:
- A 2-year prospective environmental study involving 53 buildings.
- Collection of water and biofilm samples across 6 intervals for Legionella culturing.
- Statistical analysis using prevalence ratios, adjusted for water system characteristics.
Main Results:
- Legionella colonization decreased from 60% of systems before monochloramine to 4% after conversion (PR 0.07).
- The median number of colonized sites per building was significantly reduced post-monochloramine implementation.
- Factors associated with increased Legionella prevalence included low water heater temperatures (<50°C), building height (>10 stories), and water service interruptions.
Conclusions:
- Conversion to monochloramine for municipal water disinfection is highly effective in reducing Legionella colonization of hot water systems.
- Widespread adoption of monochloramine may decrease Legionella transmission and the incidence of Legionnaires' disease in the United States.