Coronavirus Should Sharpen Focus on Another Deadly Respiratory Illness — Legionnaires’ Disease

June 10, 2020

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The unused water systems of buildings shut down by the coronavirus crisis may now be a breeding ground for the bacteria that causes the deadly Legionnaires' disease. Above, an Alabama career center closed during the pandemic. Photo: Alabama Extension, courtesy Flickr Creative Commons. Click to enlarge.

Feature: Coronavirus Should Sharpen Focus on Another Deadly Respiratory Illness — Legionnaires’ Disease

By Brett Walton

Amid the coronavirus pandemic, the respiratory disease known as Legionnaires’ has new and worrying relevance. 

Legionnaires’, which attacks the lungs, is already the deadliest waterborne illness in the United States. Discovered little more than four decades ago, the number of reported Legionnaires’ cases in the country is soaring, up more than six times since the year 2000. 

What does that look like? In 2018, there were 9,933 cases reported to the Centers for Disease Control and Prevention, which ranks Legionnaires’ disease above tuberculosis and just behind hepatitis A.

This number is most likely an undercount. An expert panel convened by the National Academies of Sciences, Engineering, and Medicine estimated the true case count, including misdiagnosed and undiagnosed cases, to be five to seven times higher. 

The death rate from the disease is about one in 10 on average, but much higher for vulnerable populations such as people older than 60, smokers and those with weakened immune systems.


Dangerous in a normal year, Legionnaires’ 

disease has new urgency in light of 

the COVID-19 emergency.


Dangerous in a normal year, Legionnaires’ disease has new urgency in light of the COVID-19 emergency.

An illness that resembles pneumonia, Legionnaires’ disease is spread by inhaling airborne droplets contaminated with Legionella bacteria. The bacteria are present in rivers and lakes, but they flourish in the built environment — specifically the nooks and crannies of building plumbing and other components of complex water systems. 

Taking root in the microbial films that grow within pipes and fixtures, the bacteria proliferate in warm water that is stagnant or has little flow. They can be aerosolized — and spread a quarter-mile or more in certain cases — by cooling towers, fountains, showerheads, faucets and hot tubs.


Unused water systems a breeding ground

Conditions this year are ripe for more outbreaks.

Due to the coronavirus pandemic, cities shut down many forms of economic activity and social life. Offices, schools, restaurants and hotels have been largely vacant for months. 

Water use in these buildings and in entire commercial districts has plummeted. The water that has been sitting in the pipes of these buildings since March could be a breeding ground for the bacteria. By now, chlorine that was added to the water after it was treated has degraded and is no longer effective at preventing microbial growth.

Plumbing researchers agree that the widespread shutdown of city commercial districts is an unprecedented event for water quality in buildings. 

The next few months will be telling.

Legionnaires’ disease exhibits both geographic and seasonal patterns. Reported cases are highest in the mid-Atlantic and Great Lakes regions, two areas that have been hardest hit by COVID-19. 

And Legionnaires’ cases peak in the late summer and early fall, a time period that coincides with states reopening their economies and their buildings.


Covering the story

Where to start? There are few local, state or federal rules regarding Legionella. The federal Safe Drinking Water Act generally covers the water that comes out of the treatment plant, leaving water quality within buildings largely unregulated (lead is an exception.) 

New York has rules for cooling towers, the rooftop units that can distribute the bacteria across neighborhoods. Other states are looking at the problem, too. But that does not mean that they are acting. Georgia considered Legionella rules in its latest plumbing code revision, but they were rejected last year. A bill in the Florida Senate to regulate cooling towers died in committee in March. 

What are your local health departments, state regulators and lawmakers doing?

One industry does have requirements: health care. Hospitals and nursing homes that receive federal reimbursements from the Centers for Medicare and Medicaid Services must have a plan for managing water within their buildings. This is because they serve the most vulnerable populations. 


Not all of the dozens of guidance documents are 

satisfactory. Even the CDC and EPA had a critical 

error about the proper temperature for water heaters.


Hotels are another high-risk sector, but one with few rules. Do the hotels in your area have a plan for addressing stagnant water before they reopen?

Industry groups and state and federal agencies are publishing guidance documents to help building owners reopen. But the quality of these guidance documents varies widely. Buildings should be flushed, but the ease of doing so depends on the complexity of the plumbing system.

Not all of the dozens of guidance documents are satisfactory. Even the CDC and U.S. Environmental Protection Agency had a critical error about the proper temperature for water heaters. That error has since been corrected.

Is there anyone in your area who is directing the outreach to building owners? What are utilities doing? They can be a facilitator. 

Also because water has also been sitting in water mains in commercial districts, utilities might need to flush their own pipes. They might need to coordinate flushing activities with building owners so that stagnant water in the mains is flushed before it gets into buildings.



For background on Legionnaires’ disease, the National Academies report is a good entry point. The expert panel made a number of recommendations for reducing the risk of Legionella. You could see if any of these recommendations have been taken seriously by your state health departments or agencies that write building and plumbing codes.

Researchers at Purdue University are tracking the building reopening guidance documents that state, local and federal agencies are publishing. They are also developing recommendations for building owners.

Industry groups are quite active in this area. The American Society of Heating, Refrigerating and Air-Conditioning Engineers published a widely accepted standard for reducing Legionella risk in large buildings with complex plumbing systems. IAPMO, a plumbing group, is another.

Legionnaires’ disease cases by state and region are reported to the CDC, which provides weekly updates. These are preliminary numbers that tend to be revised upwards in the annual accounts that are published about nine months after the year ends.

Brett Walton writes about agriculture, energy, infrastructure and the politics and economics of water in the United States for Circle of Blue. He also writes the Federal Water Tap, Circle of Blue’s weekly digest of U.S. government water news. Walton is the winner of two Society of Environmental Journalists reporting awards, one of the top honors in American environmental journalism: first place for explanatory reporting for a series on septic system pollution in the United States (2016) and third place for beat reporting in a small market (2014). He received the Sierra Club's Distinguished Service Award in 2018. Walton lives in Seattle, where he hikes the mountains and bakes pies.

* From the weekly news magazine SEJournal Online, Vol. 5, No. 23. Content from each new issue of SEJournal Online is available to the public via the SEJournal Online main page. Subscribe to the e-newsletter here. And see past issues of the SEJournal archived here.

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