Legionnaires' disease (LD) is recognized as an important hospital-acquired disease. Despite the several methods available, the optimal method to control hospital-acquired LD is not well established and their overall efficacy requires further evaluation.

To systematically review all controlled trials evaluating the efficacy of interventions to prevent hospital-acquired LD in patients at high risk of developing the disease and its effects on environmental colonization.

A database search was performed through PubMed and the Cochrane Central Register of Controlled Trials (inception-November 2014). Eligible studies included all controlled studies evaluating interventions to prevent hospital-acquired LD in patients at high risk or evaluating the effect on environmental colonization. Both individual and pooled risk estimates were reported using risk ratio (RR) and 95% confidence intervals (95% CIs).

There were no studies evaluating the risk reduction in hospital-acquired LD, but 4 studies evaluated the influence of copper-silver ionization and ultraviolet light in the reduction of environmental reservoirs of Legionella. The meta-analysis showed a significant 95% risk reduction of Legionella positivity in environmental samples using copper-silver ionization (RR, 0.05; 95% CI, 0.01-0.17) and 97% risk reduction with ultraviolet light (RR, 0.03; 95% CI, 0.002-0.41).

The best available evidence suggests that copper-silver ionization and ultraviolet light are effective in reducing Legionella positivity in environmental samples. Nevertheless, the low quality of evidence weakens the robustness of conclusions.