Legionnaires’ Disease is on the Rise: Here’s What Can Be Done

Published by Donald B. Snell and Nate Sanders on November 6, 2018

While Legionnaires’ disease has been identified since 1976, it's only come to the forefront for many facilities nationwide over the last couple of years. The increased attention began in earnest after the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) came out with Standard 188. Following up on that, the Centers for Medicare & Medicaid Services (CMS) came out with their edict that facilities currently receiving Medicare aid or payments needed to develop a water management program in order to keep receiving funds. This mandatory guidance was a governmental response to the lack of widespread adoption of water management plans.

Figure 1

Figure 1


The data in the Figure 1 graph was compiled by government agencies that track disease trends. Over the past 15 years, the incidence of Legionnaires’ disease has risen substantially. A variety of factors come into play as to why this may be so. The population is aging, which means there are more at-risk individuals. Additionally, building infrastructures are also aging - specifically in this case, plumbing infrastructures - and are not always maintained as they should be. Another often overlooked but likely culprit is water flow reduction measures, such as low-flow or no-flow water systems.

The CDC and epidemiologists are crediting improved diagnostic, testing, and reporting practices as a big part of the visible increase, but still believe that Legionnaires’ disease is vastly underreported because it is often classified as a bronchitis or pneumonia. In order for this disease to be classified correctly, specific testing and diagnosis must be done from a Legionnaires’ disease standpoint.

In June 2017, the CDC published insightful vital statistics on Legionnaires’ disease. According to the CDC report, 76% of Legionnaires’ cases stem from healthcare-acquired infections. To extrapolate this statistic using the last reported information that the CDC put out in 2015, about 6,000 cases were reported in the United States that year. In more than 4,500 of those cases, the victim acquired Legionnaires’ disease due to the environment in a hospital or healthcare facility. Out of those estimated 4,500 cases, 25% resulted in death due to the disease itself or some complication. That means just over 1,100 people died in 2015 because of a healthcare-acquired infection of Legionnaires’ disease. When numbers are laid out like this, the impact becomes more evident and the magnitude of the problem becomes eye-popping.

The biggest takeaway from this sad statistic is that 80% of those healthcare-associated infections could have been prevented by effective water management plans. That is likely the impetus behind the fact that one month after the CDC report, the CMS came out with their statement requiring all healthcare facilities receiving money from the government to put a water management plan in place in an effort to limit the number of infections and deaths caused by Legionnaires’ disease.

Where does Legionella Reside?

In potable water systems, Legionella resides in biofilms. Supported by the organic matter present in water, this biofilm typically starts forming in corroded piping and dead legs. It can also be found on filters, piping, elbows, and anywhere there is an edge or a dead leg where water has a low flow or does not flow. The biofilm builds up and eventually breaks off, with Legionella bacteria eventually making its way into your drinking water. The older your plumbing, the more likely it is that the biofilm is present.

Figure 2

Figure 2

Unfortunately, drinking water is the ideal temperature for optimal bacterial growth. The data in the Figure 2 graph was pulled from various organizations that have researched and published information about Legionella growth temperatures. For the most part, the optimal temperature for Legionella growth ranges from 77℉ to 118℉. That range is precisely where hot water temperatures run in plumbing systems, making them conducive to bacterial growth.

Once temperatures reach 122℉ or higher, the water temperature actually kills the Legionella bacteria. When temperatures start getting down below 77℉, Legionella can still be present but is typically not viable. We have personally inspected cold water samples at 46℉ that had Legionella present, though it was not proliferating at that point.

Most facilities, especially healthcare facilities, struggle to achieve an adequate hot water temperature that will both kill off bacteria but also refrain from accidental scalding and keep operational costs reasonable. Is there an ideal hot water temperature? Temperatures around 125℉ will kill off Legionella bacteria but should still be a safe enough temperature to prevent scalding.


Low-flow and no-flow water systems, especially urinals, are on the rise due to an attempt to increase water savings. More and more buildings, whether new construction or renovation, are trying to implement these savings. The question to be asked is whether the adoption of such systems will increase the growth of Legionella bacteria.

Some research points to the fact that within 72 hours, the proliferation of bacteria and organic carbon levels inside certain plumbing systems can provide the environment for Legionella bacterias and biofilms to grow. That means even chlorinated water from a municipality is not effective against these biofilms when stagnant water has had time to sit. Low-flow systems are increasing the amount of time water is in a building, thus potentially increasing the risk of Legionnaires’ disease. The take-home is if a water system has any stagnation or potential stagnation, it should definitely incorporate some type of water management program.

Successfully Manage the Risk and Prevent Outbreaks of Legionella Bacteria

A Legionella outbreak can be devastating to a facility, from both human impact and expense to medical claims and litigation which must be resolved. If a health department designates an outbreak, the resolution can take months and even up to a year. If a healthcare infection control practices advisory committee gets involved, their process can take up to six months to clear a facility. That amount of time is very impactful.

From a budgeting standpoint, both hospital line items and compliance with ASHRAE Standard 188 must be considered. Accreditation of the facility and certification of the infection preventionists must be included. Budgets for operations and maintenance are a given. For new construction, additional costs include environmental services, design and design components (such as analysis of building water systems, or peer reviews), construction commissioning, flushing, and disinfection (Depending on the schedule, more than one round of flushing and disinfection may need to be built in to effectively mitigate risk.) Contingency and emergency plans also must be considered. External stakeholders in the process will expect budget allowances to properly execute the work.

A transformational shift in healthcare design is taking place in order to comply with ASHRAE Standard 188. Architects are going to need to make their facility designs more patient-centric regarding Legionella prevention.

ASHRAE Standard 188 is a voluntary consensus standard unless incorporated into building codes. Its purpose is to establish minimum Legionellosis risk management requirements for building water systems. It is intended for multi-disciplinary and designated teams, and includes a normative annex A specifically for healthcare facilities.

While the above explains what ASHRAE Standard 188 is, here is what it is not. It does not provide recommendations for temperature or disinfection. It does not provide guidance on emergency remediation or action plans for cases of disease. It also does not require Legionella testing to be performed; instead, the standard leaves that up to the team to consider.

The CDC's toolkit contains other important standards and guidelines regarding developing a water management program to reduce Legionella growth and spread in buildings.

The other component in minimizing Legionella risk is implementing a building-specific water management program. This would identify teams, outline water flow, identify control points and parameters, implement monitoring requirements or guidelines, and provide for periodic review.

Industry non-consensus is creating more questions and contributing to gaps in what should be done to prevent Legionella. For example, not all building codes require the same water temperature. Moreover, end use may determine water temperature beyond what the building codes require. As mentioned previously, ASHRAE 188 does not provide temperature requirements.

Some non-consensus also exists between and within national organizations. For example, there is a tug-and-pull issue going on right now with the American Society of Home Inspectors (ASHI) urging the CDC to avoid additional healthcare requirements on Legionella. In the case of ASHRAE, which develops standards written in code language that must be adopted, Standard 188 covers Legionella while Standard 189.3 deals with the sustainability standard for healthcare. There are certainly different agendas fueling each of those standards, which creates further gaps and non-consensus.

The requirements for multi-disciplinary approaches with designated teams mean a host of different individuals with various responsibilities and tasks are involved - from infection preventionists and designers to commissioning agents and subject matter experts. Based on this stakeholdership of responsibility and the required documentation that is part of a water management program, we have found the use of a responsibility matrix to be very effective. Such a tool outlines the primary responsibility or task for each stakeholder, advises or assists in these responsibilities and tasks during the process, and reviews them at the end.

Golden Nuggets

We would like to point out several golden nuggets about Legionella prevention that are often overlooked. The first one is that from our field experience, the biggest impact on minimizing risk and controlling cost is early-stage input and influence on a project. Whether the project is design, construction, renovation, or repair, the earlier the influence is imparted, the greater ability there is to make a difference.

The next golden nugget is the adoption of the responsibility matrix for each designated team member. The ability to add a subject matter expert is critical here, since a healthcare facility may not have all the necessary individuals on staff to be able to address all the responsibilities. For example, building water systems vary substantially in design and capability in transmission of Legionella. Accordingly, designers have more responsibility now than they traditionally have had in the past.

Another important nugget is that the influence of ASHRAE standards for sustainability, such as codification of green, have to be considered and compared against the agenda of minimizing Legionella.

Lastly, cold-water systems contain a hidden risk of Legionella. Though they might not be at the forefront of concern, they can certainly allow Legionella transmission depending on their routing through unconditioned spaces, temperature stratification, hot water generator storage tanks, and being heated in a certain way.

Consider what effective steps to take to successfully manage the risk and prevent outbreaks of Legionella bacteria. These golden nuggets can aid in developing your next risk assessment plan, factoring in energy savings, the implication of census fluctuation, the impact of environmental service procedures, construction renovation, and operations and maintenance concerns.