Experiences of the First 16 Hospitals Using Copper-Silver Ionization for Legionella Control: Implications for the Evaluation of Other Disinfection Modalities

JANET E. STOUT, VICTOR L. YU
CAMBRIDGE UNIVERSITY PRESS, INFECTION CONTROL AND HOSPITAL EPIDEMIOLOGY, AUGUST 2003

Introduction
This study examined 16 acute care hospitals using copper-silver ionization as a disinfection method. Surveys were deployed in 1995 and 2000 to gather information from each hospital. The 2000 survey was up to 11 years after installation for some hospitals.

Results
Before installing a copper-silver ionization system, all 16 hospitals had reported cases of hospital-acquired Legionnaires’ disease. Seventy-five percent had tried other disinfection methods, including superheat-and-flush, ultraviolet light, and hyperchlorination.

After installing a copper-silver ionization system, no cases of hospital-acquired Legionnaires’ disease were reported, and the Legionella positivity rate (percentage of test sites within the hospital positive for Legionella) was significantly reduced.

• Before installation: 47% of the hospitals reported a Legionella positivity rate of 30% or higher
• 1995 (zero to six years after installation): 50% of the hospitals reported a Legionella positivity rate of 0%
• 2000 (five to 11 years after installation): 43% of the hospitals reported a Legionella positivity rate of 0%

The study found that the infection control practitioners rated the disinfection system as “excellent.” The engineers rated the operation and maintenance of the system as “average” (not easy, but also not difficult).

Conclusion
The team behind this study developed a standardized, evidence-based approach to assist hospitals with evaluating different disinfection methods. The four criteria a disinfection method must meet include the following:

1. Proof it kills Legionella in a lab study.
2. Anecdotal reports of it controlling Legionella in individual hospitals.
3. Peer-reviewed reports of it controlling Legionella in individual hospitals over a prolonged period.
4. Confirmatory reports of it controlling Legionella in multiple hospitals over a prolonged period.

At the time of this study, copper-silver ionization was the only disinfection modality to have fulfilled all four evaluation criteria.