Legionnaires' Disease: What is Legionella?

In recent months, rumors have started to circulate about a certain respiratory disease, and it's important to understand the real facts.

No, we're not talking about COVID-19. We're talking about Legionnaire's disease.

Like the novel coronavirus, it can land you in the ICU, and you'd probably never heard of it before the spring of 2020. But that's just about where the similarities end.

What is Legionnaires' Disease?

Legionnaire's disease is a lung infection that can progress into a severe form of pneumonia.

You contract Legionnaires' disease by inhaling water or mist contaminated with Legionella pneumophila bacteria, sometimes also referred to as Legionnaires' disease bacteria (LDB).

In addition to Legionnaires' disease, L. pneumophila also causes a flu-like illness called Pontiac Fever. Together, these diseases are collectively referred to as legionellosis.

How Common Is Legionnaires' Disease?

According to OSHA, there are 6,000 reported cases of Legionnaires' disease every year in the United States, but Legionnaires' is difficult to diagnose. The most recent population-based study estimated that between 8,000 and 18,000 people are hospitalized with Legionnaires' every year. Even more are exposed but experience milder symptoms.

Who is At Risk for Legionnaires' Disease?

Research has shown that in an outbreak, less than 5 people in 100 that are exposed to contaminated water will develop Legionnaires' disease. Most people have natural resistance.

However, some people have lower resistance and they're more likely to develop severe symptoms. That includes anyone who:

• Heavily smokes cigarettes
• Has chronic lung disease or diabetes
• Has received an organ transplant
• Is on renal dialysis
• Takes corticosteroids
• Has a weakened immune system (including the elderly)

Is Legionnaires' Disease Serious?

Legionnaires' disease is treatable with antibiotics, but one in 10 people who contract it will die. Others suffer long-term impairments. One study found that fatigue, neurological symptoms, and neuromuscular symptoms persisted for months in more than 60% of survivors.

How did Legionnaires' disease get its name?

Legionnaires' disease was discovered in 1976 after 200 members of the Pennsylvania American Legion (and other visitors to the same hotel) became ill with respiratory symptoms during a convention. After this outbreak, the CDC identified the causative bacteria and named it after the conventioneers.

Does that mean Legionnaires' disease is a new disease?

Legionnaires' disease undoubtedly existed before the 1976 outbreak, but we didn't understand the cause of the illness. Older cases would have been marked down as unspecified pneumonia.

How is Legionella Transmitted?

Legionella is transmitted by exposure to contaminated water. You might inhale aerosolized Legionella pneumophila from a contaminated water source, or you might aspirate contaminated drinking water.

Is Legionnaires' Disease Contagious?

Legionnaires' disease is infectious (caused by a pathogen) but NOT contagious (spread from person to person).

Outbreaks can happen when multiple people are exposed to the same contaminated water source, but there is no evidence that the bacteria can be transmitted from an infected person to others.

The fact that most cases are sporadic and not associated with a larger outbreak supports this conclusion.

Where Do You Find Legionnaires' Disease Bacteria (LDB)?

Legionella pneumophila is very common in the environment, but it's really only dangerous when it's allowed to reproduce in warm water.

In natural water sources like freshwater lakes, streams, and ponds, Legionella levels are naturally occurring but low enough that you're very unlikely to get sick.

But when Legionella finds warm stagnant water (68°-122°F), it can multiply to dangerously high levels. It breeds the fastest in water that's between 90° and 105°F and contains rust, scale, and other microorganisms.

That's why the source of most Legionnaires' disease cases are manmade containers and systems where water sits motionless for extended periods of time.

What are the Most Common Sources of Legionella Infection?

Cooling towers, evaporative condensers, evaporative coolers (also known as swamp coolers), water heaters, and humidifiers provide the ideal conditions for Legionella growth. Transmission is facilitated when they aerosolize potentially contaminated water (either directly or through appliances like misters, sprinklers, showers, jacuzzis, and whirlpool baths).

Can I Get Legionnaires' Disease From My Home Water Heater?

It's possible, but a small home water system is less likely to be a breeding ground for Legionella than the systems you find in large buildings. That includes hotels, commercial facilities, and multi-family residences like apartment buildings. There have also been outbreaks on cruise ships, where poorly maintained freshwater systems can breed and transmit the bacteria.

Legionnaires' Disease and COVID-19

COVID-19 is the main reason Legionnaires' has suddenly gotten more ink. The symptoms are similar on the surface, but that's not the reason.

There have been questions about whether certain coronavirus precautions can increase your risk of contracting Legionella.

Can Face Masks Give You COVID-19?

From early in the spring, there have been rumors that you can get sick with Legionnaires' disease from mask-wearing.

Luckily, it's not true (or even theoretically possible).

While Legionella is transmitted by water droplets, it can't be transmitted through respiratory droplets (water droplets exiting infected lungs). Remember when we said Legionella can't be transmitted from person to person? That's important here.

Even if Legionella was found in respiratory droplets, it couldn't survive on dry surfaces like cloth or paper masks.

The only mask-related Legionella transmission on record involved a sleep apnea machine that was directly connected to a contaminated water system. These were completely different conditions than you'd experience with a pandemic mask.

Could Other COVID-19 Precautions Increase Legionnaires' Risk?

Actually, yes, which may be why Legionella got traction in the news at all.

In May, the CDC warned that Legionella (and other waterborne pathogens) could grow in the plumbing systems of large buildings that were closed due to COVID-19 lockdowns. Without regular use, water in pipes and tanks could sit stagnant at the ideal temperature. Plus, disinfectant measures were, in some cases, allowed to lapse.

It's a preventable issue, however. The CDC published detailed plans for building managers on how to sanitize water systems before occupants returned.

What are the Symptoms of Legionella?

The early symptoms of Legionnaires' disease are similar to the flu. Within a few days, patients experience more severe symptoms, particularly if their immune systems are too weak to stop the infection before it gets that far.

What are the Early, Flu-Like Symptoms of Legionnaires' Disease?

Early symptoms of Legionella include a slight fever, headache, body aches (joints and muscles), a lack of energy, and a loss of appetite.

What are the Legionella Pneumonia Symptoms?

In the pneumonia phase of Legionnaires' disease, symptoms include a high fever (102° to 105°F), a cough that starts dry but later produces phlegm, shortness of breath / difficulty breathing, chills, and chest pains.

Early treatment of Legionnaires' is the key to a successful recovery, so you should seek medical treatment as soon as you notice these symptoms.

What is the Treatment and Recovery Process for Legionnaires' Disease?

The earlier you get treated for Legionnaires' disease, the better off you'll be. That's even more true if you have a compromised immune system.

However, many hospitals can't test directly for Legionella pneumonia, so it's important to tell your doctor if you have any reason to suspect you've been exposed – for example, you recently took a cruise or enjoyed a hotel jacuzzi. Symptoms would typically start within 2-10 days of exposure.

How is Legionnaires' Disease Treated?

The most common Legionnaires' disease treatment is macrolide antibiotics like azithromycin, erythromycin, and clarithromycin. The macrolide class of antibiotics can treat other strains of bacterial pneumonia as well, so it's commonly prescribed for suspected cases.

How Long Does It Take to Recover From Legionnaires' Disease?

As discussed, Legionnaires' patients often suffer from related symptoms for months, but most survivors recover completely within a year.

Preventing Legionnaires' Disease

An ounce of caution can save vulnerable populations from a painful illness and expensive hospital bills. There are a few groups of people that have the power to prevent a Legionnaires' outbreak: building managers, maintenance staff, and certain employers.

The most common structures associated with Legionella are hospitality businesses (hotels, resorts, and cruise lines) and healthcare facilities (hospitals, long-term care facilities, and dentists). However, according to OSHA, those two industries only comprise 27% of all cases, so Legionella exposure can occur anywhere under the right conditions.

The safety of your water systems are an important part of your maintenance plan and risk assessment for any building or vessel. Some examples of measures for Legionnaires' prevention include:

• setting commercial-grade water heaters to 140°F or above (not recommended for single-family appliances)
• routinely checking for biofilms in the water system
• sampling for Legionella and other waterborne pathogens
• closely monitoring storage tanks and infrequently used components where Legionella growth is likely
• properly flushing out water systems in structures that have been dormant

By taking these measures – and by properly leveraging your continuing education in occupational safety and health, property management, or building maintenance – you can reduce liability and save lives.