Q&A: Legionnaires' Risk Management

July 2, 2020

This article originally appeared in the July 2020 is as "Legionnaires' Risk Management"

About the author:

Thomas Bernier is partner for the Baltimore Office of Dehay & Elliston. Bernier can be reached at [email protected].


WQP Associate Editor Cristina Tuser interviewed Thomas Bernier, a partner at the Baltimore Office of Dehay & Elliston, about legionella risk management as water conservation and public health becomes an increasing issue. 

Cristina Tuser: Have you noticed an increase in recent years of Legionnaires’ outbreaks? 

Tom Bernier: 95% of the Legionnaires’ disease are considered sporadic. So, the vast majority of cases are considered sole sporadic cases that no one really links to a specific source. With respect to the number of cases over the last few years, there is a number of data on that. The number of cases has steadily and definitely increased over the past few years and decades. In 2018, which is the last set of numbers reported from the U.S. Centers for Disease Control and Prevention (CDC), they reported 9,933 cases, which is a 540% increase between 2002 and 2018. 

Depending on where the Legionnaires’ is hitting—primarily where there is a target of susceptible people—the rates can get pretty high, like in nursing homes and in hospitals. For years, the CDC has published their belief that the number of cases is underreported. They always used the estimated range of 8,000 to 18,000 cases a year. Which is interesting, because in 2018, we had approximately 9,900, which is the first time we have seen the actual number of reported cases exceed their low end estimate range of 8,000. The trend is still heading up.

Tuser: What are contributing factors to these increases?

Bernier: I think it breaks down to three categories. I think number one would be awareness and vigilance. Doctors now are more often looking for it in hospitals and emergency rooms. They are consciously looking for it now and more often. There are also a few extra tests available. For example, the urinary antigen test for legionella, which is pretty fast, easy and cheap.—this will only test for one type of legionella bacteria and one strain of legionella (LP1), but as it turns out, that bacteria and strain are the most common. 

The second contributing factor is that we have a growing population of susceptible people. Anyone that is immunocompromised for any reason can get sick. We have all these new medical prescription therapies that treat immuno-based illnesses by suppressing the immune system, and as a result you have a great resulting susceptible population. 

The third category is environmental. Legionella is a modern plumbing disease and as our society gets more into conservation, a lot of places are lowering their water temperatures. Water that is stagnant, stored and sitting that contains even the lowest levels of undetectable levels of legionella bacteria, can sit there long enough for the legionella to amplify.  It comes in through municipal water, which is a proven source of bacteria in many places. Essentially, modern conservation issues are a double-edged sword.

Tuser: How can building managers prepare to fight legionella contamination? 

Bernier: Managers should understand the critical water features of the building. Does your building have a cooling tower? Does it have a pool, a lobby with a water feature? What is the population of your building? Who is residing there? These are all factors you should understand. How long does your water sit and how fast does it travel? You have to have a documentable water management plan. 

There are those that say there needs to be writing, there needs to be a checklist and so-forth. This is how you can maintain fountains, spas, hot tubs, etc. There is no perfect or exact plan, since every building has different needs. The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Standard 188, however, establishes minimum legionellosis risk management requirements for building water systems. A building manager needs to be aware of local statutes that would apply. In New York, for example, there is a statute that requires every cooling tower to be registered and tested for the presence of legionella. Anyone who is practicing water safety of management needs to do homework to see whether there are any guidelines already in place. 

*Responses have been edited for clarity.

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