The authors’ major 2011 review of all of the existing modalities for remediation of Legionella, published in Infection Control and Hospital Epidemiology, found that copper-silver ionization appears to be the best available technology today for controlling Legionella colonization in hospital water systems when both ion levels and Legionella cultures are monitored.
If a systemic disinfection system is installed because of occurrence of resident cases, then copper-silver ionization may be the preferred approach given its established track record, especially if the news media have reported the outbreak.
Chlorine dioxide, a synthetic gas, was first used for Legionella control in Europe, where it generally failed. The Special Pathogens Laboratory at the Pittsburgh Veterans Affairs Health System published the first successful controlled evaluation for L. pneumophila in the United States at Geisinger Medical Clinic in Pennsylvania, where it worked.
Maintaining a sufficient residual concentration of chlorine dioxide in the hot water system is challenging. Elevated temperature hastens the conversion of chlorine dioxide to chlorite, which may lead to deleterious health issues. An effective residual of the gas must be maintained throughout an extensive water distribution system.
The decay of chlorine dioxide depends on the water temperature and the distance from generation site to the distribution system. Given its rapid decay in hot water, a higher concentration of chlorine dioxide must be injected at the source to reach an effective concentration at the distal site. Thus, the efficacy of chlorine dioxide may be limited to only cold water supplies, not hot water recirculating lines. The advantage of chlorine dioxide is its lower cost compared to copper-silver ionization for the same capacity.
Conversely, the most prominently used solutions—hyperchlorination and heating and flushing the water distribution system—have significant drawbacks. The first three hospitals in the United States to try hyperchlorination discontinued the practice because it failed to control Legionella and corroded water pipes. Heat and flush is often an effective short-term fix in cases of an outbreak. Vendors experienced with this method should oversee the process, as it invariably fails if healthcare facility personnel oversee the process. Infection control practitioners need to document the temperature at the tap and duration of the flush.
Ineffective (and expensive) control measures
If a consultant suggests either of the following expensive control measures, management should think again, because the recommendations are not only ineffective but logistically tedious to implement and expensive.
- Cleaning of distal outlets. Faucets and showerheads are disinfected by immersion in chlorine of high concentration or boiling water. Or these outlets are replaced with new ones. This method only eradicates the Legionella at the outlets, a small proportion of the total Legionella in an existing plumbing system. Legionella can reappear within days or weeks because it is still present throughout the plumbing system.
- Removing dead legs (unused sections of water pipes). The concept of a “stagnant” aquatic environment in which Legionella readily propagates is an appealing one. Scientific evidence supporting this concept is lacking, however.
In summary, Legionnaires’ disease is under-diagnosed in nursing homes. When it is discovered, it may be in the context of an outbreak. If deaths occur, panic during the outbreak and exorbitant costs from litigation can occur.
A major benefit of infection control participation is the avoidance of poor decision-making during an outbreak. Inexperienced consultants and healthcare facility managers often make costly and useless recommendations to management. Prevention can be low-cost and effective. We now are applying a new approach for nursing homes and other LTC facilities that should be more effective, easier to operate and must less expensive than installing a permanent disinfection system.
The impending ASHRAE 188P standard and growing awareness among regulatory bodies may be the tipping point for LTC providers to take immediate steps to find out their risk exposure and act to prevent outbreaks in the name of resident safety.
Yusen E. Lin, PhD, MBA, is visiting professor of civil and environmental engineering at the University of Pittsburgh and a professor and director of the Center for Environmental Laboratory Services at the National Kaohsiung Normal University in Taiwan. Victor L. Yu, MD, is a professor of medicine at the University of Pittsburgh and medical director of the Special Pathogens Laboratory in Pittsburgh.