The Links Between Covid-19 and Legionnaire’s Disease

Marissa Newby
Legionella PneumophilaWikimedia Commons

It is 1976, you and a couple thousand of your friends are attending a convention in Philadelphia to celebrate the signing of the Declaration of Independence. What could go wrong?

Turns out, a lot can go wrong. If I had changed the date to 2021 and you are reasonably capable of logic, you would be acutely aware of the impending threat of catching Covid-19 in a large group. In 1976, the HVAC system to your hotel room would have been the reason for your crippling pneumonia a few days after you returned home.

A few days after you get back, your friends start dying suddenly. At first, it seems like a curious epidemic of heart attacks until doctors contact the CDC to investigate what they believe is a pneumonic outbreak. The long path to identifying the pathogen would leave lives in its wake but teach us a great deal about the Legionella bacterium.

The culprit of the 1976 outbreak was the hotel’s HVAC. However, this was not the first outbreak, nor would it be the last. In 1965 there was an outbreak of pneumonia at St. Elizabeth’s Hospital in Washington DC that killed 16 of the 78 infected. In 1967 there was an outbreak of “Pontiac Fever” at a health department in Michigan, although there were no fatalities. 1974 saw an outbreak at the same hotel, 2 of the 20 patients died.

Why Is This Pertinent to Covid-19?

Legionella tends to grow in condensers, HVAC systems, water storage and warm freshwater sources. Ambiently, in lakes and rivers, legionella usually does not exist in a high enough concentration to get anyone sick. The average temperature that legionella gets cozy in is about 90 degrees Fahrenheit. However, stagnant water contained in piping that interfaces most often with humans is a breeding ground for legionella.

After several months, even a year, of office spaces and industrial HVAC systems being shut down or operating at a diminished capacity, returning to work could be a slightly dangerous prospect. The condensers, piping and traps in these systems tend to harbor bacteria, this is not unknown. Many systems, especially those attached to healthcare facilities, filter the majority of these pathogens. However, healthcare facilities haven’t been closed. Hotels, resorts and office buildings have been closed while people are on travel restrictions and working from home.

Stagnant water can grow algae, proliferate amoeba and other protozoans, biofilms and sediment. The warm, uncirculated water in inactive HVAC systems can be a cozy home for legionella. The CDC has detailed recommendations, risks and hazard analysis for reopening and resuming building occupany after shutdown and stagnant operations.

Covid-19 Can Mimic Legionnaire’s Disease

The initial symptoms and presentation of both Covid-19 and Legionnaire’s disease are eerily similar. We are testing for Covid-19, but commonly testing for Legionnaire’s disease is typically not conducted. Testing exists, but it is easy to assume with the frequency of on particular infection that other things are reasonably ruled out.

Resource limitations and capacity issues can sometimes lead to a standard where reasonable assumptions are made, symptoms are treated and wide-sweeping treatments become common practice. In hospital systems that are already overwhelmed with pandemic illness, the more responsible assertion is that a group of people with similar symptoms are likely suffering the same illness. Understanding common diagnostic practices during pandemic illnesses, you can probably see where other diseases are lost in translation.

The treatment plans for Legionnaire’s and Covid-19, however, are primarily different. The pathogens are different. Legionnaire’s disease is bacterial whereas Covid-19 is viral. Atypical pneumonias caused by these diseases are categorically different in treatment, but not that different in persistence. Covid-19 patients and Legionnaire’s patients tend to have stubborn, long-lasting pneumonia. Mucosal sampling is the key differentiator for diagnostic purposes, in addition to antibody testing.

The landscape of fighting illnesses is dynamic. Identifying pathology can sometimes be done after the fact. Legionnaire's Disease is likely underdiagnosed in the United States with roughly 10,000 cases reported in 2018. Certain disease pathologies are incredibly similar, even if they have fundamentally different causes. Be cautious, remain masked, use good hygiene practices and be self-aware. All of these actions can help prevent both diseases.

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Marissa, a graduate safety practitioner and paramedic, has been writing and editing fiction and non-fiction work for 15 years. She delivers researched and sourced news concerning world events, public health, public safety and emergency management.


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