Infection Control and Hospital Epidemiology

[About Infection Control and Hospital Epidemiology] [Table of Contents

Volume 19 (12) * December 1998 * Original Article (abstract)

Controlling Legionella in Hospital Water Systems:
Experience With the Superheat-and-Flush Method and Copper-Silver Ionization

Janet E. Stout, PhD; Yu-Sen E. Lin, MS; Angella M. Goetz, MNEd; Robert R. Muder, MD


To evaluate the effect of copper-silver ionization on Legionella colonization and nosocomial legionnaires’ disease and to compare the efficacy of metal ions versus the superheat-and-flush method of disinfection.


Prospective determination over a 36-month period of copper and silver ion concentrations in the recirculating hot-water system, Legionella colonization of the hospital water distribution system, and cases of nosocomial legionnaires’ disease. Retrospective comparison of results with the previous 13 years, during which the superheat-and-flush method was used.


The Pittsburgh Veterans’ Affairs Health Care System (University Drive Division) acute-care hospital.


Three copper-silver ionization systems were installed on the hot-water distribution system in November 1994.


The average number of cases of legionnaires’ disease per year and the percentage of distal sites positive for Legionella pneumophila for the superheat-and-flush method versus the copper-silver ionization method was six cases with 15% positivity versus two cases with 4% positivity, respectively. The reduction in Legionella colonization after copper-silver ionization was significant (P<.05) compared to the superheat and flush. Mean copper and silver ion concentrations (mg/L) were 0.29 and 0.054 from hot-water tanks, and 0.17 and 0.04 from distal outlets, respectively.


We conclude that a properly maintained and monitored copper-silver ionization system was more effective than the superheat-and-flush method for reducing the recovery of Legionella from the hospital water distribution system (Infect Control Hosp Epidemiol 1998;19:911-914).


From the Special Pathogens Laboratory and Infectious Disease Section (Drs. Stout and Muder; Mr. Lin and Ms. Goetz), Veterans’ Affairs Pittsburgh Health Care System, University Drive Division; the University of Pittsburgh School of Medicine (Drs. Stout and Muder), Pittsburgh, Pennsylvania.

Address reprint requests to Robert R. Muder, MD, VA Medical Center, Infectious Disease Section, University Drive C, Pittsburgh, PA 15240.

The authors thank Max Dorosa, Randy Bushaw, and Edward Cipriani for engineering assistance, and Shirley Brinker for secretarial assistance.

97-OA-136. Stout JE, Lin Y-SE, Goetz AM, Muder RR. Controlling Legionella in hospital water systems: experience with the superheat-and-flush method and copper-silver ionization. Infect Control Hosp Epidemiol 1998;19:911-914


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