Lessons for Legionella Prevention: 23 Years of Johns Hopkins Hospital Data

It was around 20 years ago that I met Greg Bova, who at that time was working in facilities management at Johns Hopkins Hospital (JHH).

Since then, Greg and I have had many conversations, most of them on the phone and a few in person. In addition to his genuine interest in providing safe water for his employer’s patients, Greg has contributed to public health more broadly by sharing insights from his experience in managing JHH water systems.

Greg has gathered a lot of data! He has always been meticulous and thorough in testing ideas before and after implementing them. So, I was excited to find out Greg’s team was sharing 23 years of data on their water systems.

The published papers, titled “The results of chlorine dioxide use after 23 years,” parts 1 and 2, are about much more than chlorine dioxide (ClO₂). The physical system changes that accompanied chlorine dioxide treatment are a classic example of Legionella risk management: Instead of trying to pin Legionella findings on one cause and looking for a silver bullet solution, the hospital took a step-by-step approach that involved, over time, several physical and operational changes to their water systems, along with ClO₂ treatment.

Their efforts were successful. Legionella positivity (percentage of potable water system samples in which Legionella was found) and concentrations were reduced over the 23-year study period. In the last four years of the study period, no Legionella was detected. The papers provide a building-by-building breakdown of the results.

Chlorine dioxide treatment for Legionella control

The hospital began chlorine dioxide (ClO₂) treatment in 2001. For the first 10 years or so, ClO₂ was injected only into the cold-water system (near the point of building entry) with the goal of maintaining a residual throughout the potable water system, including the hot water. Around 2012, the hospital began injecting ClO₂ into the hot-water system as well as the cold. Adding the second injection point just downstream of the water heaters resulted in higher (more effective) ClO₂ residual levels in the hot water, better control of ClO₂ levels in both the hot and cold systems, and reduced Legionella findings.

0.5 ppm (mg/L) was found to be the optimum dosing concentration of ClO₂. Dosing was automated based on sensor-monitored data.

Pipe Corrosion and Investigations

After finding pinhole leaks in copper piping, the hospital sent multiple samples to laboratories to determine the cause. The leaks were found to be caused by either chlorine, chloride, pipe flux, or high water velocities. Although ClO₂ was not identified as the direct cause of the leaks, it may have contributed by removing biofilm and thereby exposing the pipes to direct contact with chlorine and chloride, accelerating corrosion.

System Changes That Made a Difference

As with other chemicals used for supplemental disinfection, the success of ClO₂ treatment in reducing Legionella and other pathogens in potable water systems depends in part on the design, operation, and maintenance of the systems. The papers report many physical and operational changes that Johns Hopkins Hospital made during the study period, including the following:

• Faucets and showers in patient bathrooms were flushed daily. This was found to be important for maintaining a ClO₂ residual through every fixture.
• Because oversized pipes led to lower water circulation velocities, inadequate temperature distribution, and laminar flow, they were replaced with smaller pipes.
• Pumps were added, and undersized diverter valves were replaced to improve hot water circulation.
• Pumps and controls were adjusted to correct high pressure and water hammer.
• Electronic faucets were replaced with manual faucets on inpatient sinks.
• Aerators were replaced with laminar flow devices.
• Twenty-micron centrifugal filters with automatic backflush (purge) were installed on water supply lines near points of building entry.

Final Thoughts

Kudos to Greg Bova and the Johns Hopkins Hospital team for sharing their lessons learned in managing water systems for Legionella control. Their efforts provide a good example for facility managers worldwide.

For the full report, see part 1 and part 2 in Health Facilities Management magazine.

What has your facility learned about managing Legionella risk or implementing supplemental disinfection? Share your experiences in the comments or reach out to continue the conversation.