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Legionnaires Disease: Causes, Symptoms and Treatment

Published: 2014-05-26 - Updated: 2021-08-29
Author: Thomas C. Weiss - Contact: Contact Details
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Synopsis: Information regarding Legionnaires Disease including causes, symptoms, tests and treatment. While Legionnaire's disease mainly affects a person's lungs, it occasionally may cause infections in wounds or other parts of a person's body, to include their heart. Outbreaks of Legionnaire's disease can be prevented, but prevention does require absolutely meticulous cleaning and disinfection of pools, spas and water systems.

Main Digest

Legionnaire's disease is a form of severe pneumonia involving inflammation usually caused by a resulting infection. The disease is caused by a bacterium known as, 'legionalla.' People cannot catch Legionnaire's disease from person-to-person contact. Instead, the majority of people get the disease from inhaling the bacteria. Older adults, people with weakened immune systems, as well as smokers, are all especially susceptible to Legionnaire's disease.


The Legionella bacterium also causes, 'Pontiac fever,' which is a milder form of illness that resembles the flu. Separately or together, the two forms of illnesses are at times referred to as, 'legionellosis.' Pontiac fever often times clears on its own. Untreated Legionnaire's disease; however, may be fatal. While prompt treatment with antibiotics usually cures Legionnaire's disease, some people continue to experience issues even after receiving treatment.

The disease got its name as a result of an outbreak during the 1976 convention of the American Legion in the city of Philadelphia. Approximately 180 American Legion members who were attending the conference contracted a mysterious form of pneumonia that failed to respond to conventional antibiotic treatment; 29 of them died. Over time, the culprit turned out to be the Legionella pneumophila - a bacteria that was proliferating in the air conditioning system of the hotel.

Symptoms of Legionnaire's Disease

Legionnaire's disease commonly develops 2-10 days after a person is exposed to legionella bacteria. The disease frequently starts with signs and symptoms which include the following:

By the 2nd or 3rd day, a person with the disease will develop additional signs and symptoms. These signs and symptoms may include:

While Legionnaire's disease mainly affects a person's lungs, it occasionally may cause infections in wounds or other parts of a person's body, to include their heart. A mild form of Legionnaire's disease known as Pontiac Fever might cause signs and symptoms that include chills, fever, and muscle aches. Pontiac fever does not infect a person's lungs and the symptoms often times clear with 2-5 days.

Causes of Legionnaire's Disease

The bacterium, 'Legionella pneumophila,' is responsible for the majority of instances of Legionnaire's disease. Outside, legionella bacteria have the ability to survive in water and soil, yet rarely cause infections. Inside, legionella bacteria have the ability to multiply in all kinds of water system to include air conditioners, hot tubs and mist sprayers in grocery store produce departments. While it is possible to contract Legionnaire's disease from home plumbing systems, the majority of outbreaks have happened in larger buildings - maybe because complex systems permit the bacteria to grow and spread more easily.

Most people become infected when they breathe in microscopic water droplets that contain legionella bacteria. The water droplets may come from a faucet, shower, whirlpool, or water dispersed through the ventilation system of a large building. Outbreaks of the infection have been linked to a number of sources such as:

Legionella bacteria mainly spread through aerosolized water droplets. The infection can be transmitted in other ways; however, to include the following:

Risk factors

The fact is - not everyone who is exposed to legionella bacteria becomes ill. A person is more likely to develop an infection if they:

Legionnaire's disease is a local and sporadic issue in nursing homes and hospitals where germs might spread easily and people are more vulnerable to infections.


Legionnaire's disease may lead to several life-threatening complications. These complications may include the following:

If Legionnaire's disease is not treated quickly and effectively, it may be fatal. The potential for the disease to be fatal is particularly true if a person's immune system is weakened by medications or disease.

Tests and Diagnosis for Legionnaire's Disease

Legionnaire's disease is similar to other forms of pneumonia. To assist with identifying the presence of legionella bacteria quickly, a doctor might use a test that checks a person's urine for legionella antigens, which are foreign substances that trigger an immune system response. A person might also have 1 or more of the following tests or procedures:

Treatment and Medications

Antibiotics are used to treat Legionnaire's disease, to be plain. The sooner antibiotic therapy is started, the less likely the chances are a person will experience serious complications or die.

In a number of instances, treatment does require hospitalization.

Pontiac fever goes away by itself without treatment and does not cause lingering issues.

Preventing Legionnaire's Disease

Outbreaks of Legionnaire's disease can be prevented, but prevention does require absolutely meticulous cleaning and disinfection of pools, spas and water systems. Avoiding smoking is the #1 most important thing a person can do to decrease their risk of becoming infected. Smoking increases the chances that a person will develop Legionnaire's disease if they are exposed to legionella bacteria.

Author Credentials:

Thomas C. Weiss is a researcher and editor for Disabled World. Thomas attended college and university courses earning a Masters, Bachelors and two Associate degrees, as well as pursing Disability Studies. As a Nursing Assistant Thomas has assisted people from a variety of racial, religious, gender, class, and age groups by providing care for people with all forms of disabilities from Multiple Sclerosis to Parkinson's; para and quadriplegia to Spina Bifida.

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Cite This Page (APA): Thomas C. Weiss. (2014, May 26). Legionnaires Disease: Causes, Symptoms and Treatment. Disabled World. Retrieved September 22, 2023 from

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