Managing Legionella Risks When Reopening Buildings

October 9, 2020 Bob Krell

By Susan Valenti, Healthy Indoors Magazine

By Susan Valenti

Legionella Pneumophila Bacteria

Almost as soon as the U.S. went into lockdown this past spring and we realized that wearing facemasks to prevent COVID-19 were probably a good idea, there was a familiar word that was mentioned in industry circles.


Legionella is the bacteria that can grow in building HVAC and water systems, and causes Legionnaires Disease, a severe, and sometimes fatal, form of pneumonia. As re-openings of buildings continue this year, it’s important to keep Legionella top of mind. And the last month was particularly full of warnings and updated information that can help professionals and consumers navigate this important problem.

The Centers for Disease Control and Prevention (CDC) reported more than 5,000 cases in 2019. So far this year, almost 2,000 cases have been reported and that number is rising, especially in schools. In their recent weekly newsletter, the Healthy Schools Network reported on outbreaks in more than four states and advised schools and childcares to follow their state health departments advice on flushing or ASHRAE Standard 188 for managing building water systems.

A sign on the side of a road

Description automatically generatedLast month, mainstream media reported CDC had closed several buildings it leases in Atlanta, Ga., because the bacteria had been found in their water systems; most likely because of the prolonged pandemic shutdown. It was found in a cooling tower as well as in some water sources in the buildings. The General Services Administration (GSA) told CNN that “out of an abundance of caution, we have closed these [CDC] buildings until successful remediation is complete.”

Legionella bacteria are common in water everywhere. They’re usually only a problem when the water gets aerosolized and people breathe it in. Showers and fountains are common sources. The name dates back to 1976, when an outbreak among people at an American Legion convention in Philadelphia, Pa., affected 182 people and killed 29 of them.

People most at risk include the elderly, smokers, people with suppressed immune systems, and diabetics. These are the same people who are also most susceptible to COVID-19.

A CDC epidemiologist told CNN that “it’s not yet clear if the pandemic has worsened the Legionella problem,” adding that state health departments that normally monitor and report cases of Legionella infection are tied up dealing with the coronavirus. There’s currently no national entity that checks buildings to see if the bacteria has started growing in the plumbing.

The Maine Indoor Air Quality Council (MIAQC) recently presented a free webinar on Legionella Basics in a COVID-19 World last month. Dennis Francoeur, a certified industrial hygienist in Portland, Maine, provided a refresher on preventing, recognizing, testing, and control of Legionella. Topics included: AIHA guidelines on Legionella, how to identify where it might grow in buildings, and how it deal with it in HVAC systems. To get a link to the webinar replay, you can email

Legionella expert Matt Freije of HC Info in Seattle, Wash., weighed in recently with two Legionella articles for professionals during the pandemic. In “Flushing a COVID-Closed Building Won’t Solve Its Legionella Problem,” he calls the common flushing solution during a shutdown “unrealistic” because of biofilm. The other article provides four warnings about COVID-19 and building water systems. You can check out both of these articles at the website

The Alliance to Prevent Legionnaire’s Disease, a nationwide advocacy group headquartered in Washington, D.C., has also been a very strong voice during the pandemic. They recently held their first virtual conference on risks during and after the pandemic. Consumer advocate Erin Brockovich provided a call to action to raise awareness on water and Legionella issues at the event, while other experts tackled how COVID was affecting the current public health response and water management. For more information on their COVID-19 resources or to get a conference replay link, you can go to their website at www.

Finally, Dr. David Krause and Pall Medical presented a webinar last month on Facilities After The COVID-19 Pandemic. It spotlighted what to consider before and during the re-opening of healthcare facilities, hotels, and office buildings to prevent and respond to Legionnaires’ disease outbreaks.

Krause is the founder and principal toxicologist for HealthCare Consulting and Contracting (HC3) in Tallahassee, Fla. He is a recognized expert in Legionnaires’ disease, and he co-authored the 2009 Guidelines for the Surveillance, Investigation, and Control of Legionnaires’ Disease in Florida and the 2015 AIHA Guideline for the Recognition, Evaluation, and Control of Legionella in Building Water Systems. Pall Corp. is a filtration, separation and purification leader providing solutions to meet the critical fluid management needs of customers across the broad spectrum of life sciences and industry.

When quarantines and isolation orders were issued last March, buildings were closed down, either fully or partially, and this led to water systems that serve these buildings to also being effectively closed.

“Before the outbreak occurred, Legionnaire’s disease was on the rise, on the march,” Krause said. “It had been increasing for more than 15 years. The case counts went from around 1,000 in 2001 to almost 10,000 cases reported in 2018. That’s not a public health success. We need to recognize that Legionnaire’s Disease is something that prime to make a big resurgence as we reoccupy buildings that have been closed.”

Incoming Municipal Supply Water Lines – Photos by David Krause, HC3, Tallahassee, FL

Here are a few takeaways that Krause told webinar attendees:

  • The standard of care for Legionnaire’s Disease has been a moving target since before 2015. ANSI/ASHRAE 188-2018 is a voluntary standard that was finally published after 10 years of debate and consternation. It’s recommended by the CDC and moves to a proactive rather than a reactive strategy to deal with Legionella. But water management plans and programs that are compliant with ASHRAE 188 weren’t written for the situation we’re dealing with right now.
  • Current guidance recommends flushing the water– basically turn on the lines and flush a lot of water through the buildings, water lines, the hot and the cold systems. “Unfortunately, that’s not unlikely to mitigate or remediate problems that are going to happen,” Krause said. “When you experience many months of untreated water, stagnant water in your building water systems, many of the water systems that are serving your buildings have been stagnant in the water mains. You have entire communities, entire downtown business districts and retail parks that have been essentially sitting stagnant for months. So just running water through them is important to do. You may actually need to consider hyper chlorination or shock treatment of the water systems to disrupt biofilms that do develop and any bacterial colonization that arises now.”
  • Testing for bacteria takes time and money. The number of tests and samples you may have to take can be in the dozens to hundreds, and samples often costs well over a hundred dollars per sample for analysis. And for Legionella, the expected turnaround time is two weeks before you should expect results in order for a reliable test to a culture to be relied upon. There are many ways to mess up a sample collection for Legionella. 

  • Legionnaire’s Disease mimics COVID-19. The cruel irony is that individuals presenting with pneumonia, nonspecific pneumonia, like cough or fever, it doesn’t show up on a regular test at the end. And Legionnaire’s Disease is not spread from person to person.
  • COVID-19 may actually be a distraction for most building owners and property managers who are more concerned with opening up and social distancing than they are with their water systems at this point. Krause said the fatality rates for Legionnaire’s Disease far exceed those for COVID-19. “This is preventable,” he said. “It would be the building owners and operators who will bear the brunt of that prevention, not public health officials.”
  • A building owner wishing to open properly should work with their local water utility to make sure the distribution pipe is properly flushed before they begin their internal flushing and testing. Krause said that he would want the municipal water service to come out and turn on every fire hydrant in the neighborhood to help flush their lines until the point where that water is sufficiently chlorinated. So, what’s replaced the water in the lines with water that has enough chlorine to control Legionella growth. Then they either flush or hyper chlorinated flush, or test at least. But you were to get at least some level of chlorine, remember the water in the water service, it will keep clean water clean. It will not remediate contaminated building water systems.

The post Managing Legionella Risks When Reopening Buildings appeared first on Healthy Indoors.

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