Facts about Legionnaires' Disease: Causes, Symptoms, Treatment, & More

Facts about Legionnaires' Disease: Causes, Symptoms, Treatment, & More
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Legionnaires’ Disease

The following are facts about Legionnaires’ disease:


Legionnaires’ disease (also called Legionellosis) is a respiratory infection (a type of pneumonia) caused by the bacterium legionella. The bacteria was first identified in 1976 after many people at an American Legion convention in Philadelphia suffered an outbreak of this disease.

The bacteria thrives in warm, damp environments. It can be found in nature (such as in hot springs, rivers, and soil) but the levels are normally so low that rarely do they cause problems. However, it can become a real threat when it grows in warm water found in hot tubs, swimming pools, hot water tanks, cooling towers, and water/air conditioning systems in large buildings/cruise ships. The person normally becomes infected when they breathe in a mist or vapor (microscopic water droplets) containing the bacteria. It is not spread from person to person (has not been proven).

Risk Factors

Most people exposed to the bacteria do not become ill. Those at most risk of becoming ill include people who smoke, are alcoholics, are over the age of 65, have a weak immune system (such as from diseases like AIDS, cancer, kidney failure, or diabetes or from drugs that suppress the immune system like chemotherapy drugs), or have a chronic lung disease (such as COPD or emphysema). Although a person can become infected any time of the year, most illnesses occur during the summer and early fall months.


Symptoms of Legionnaires’ disease usually show up 2-14 days after being exposed to the legionella bacteria and are similar to other types of pneumonia. Symptoms include fever, chills, headache, muscle pain, fatigue, loss of appetite, nausea, vomiting, diarrhea, lack of coordination, cough (which may bring up mucus or even blood), chest pain, and shortness of breath.


Tests include a chest x-ray to confirm pneumonia and usually a urinalysis to confirm the bacteria. Lung tissue, sputum (phlegm), and blood can also be used to diagnose the condition.


Legionnaires’ disease can be fatal but most cases can be successfully treated with antibiotics. The sooner it is diagnosed and treated, the better the outcome.


Complications include respiratory failure, septic shock, and acute kidney failure.

More facts about Legionnaires’ disease include:

• Although inhaling water droplets is the primary way of becoming infected, other ways include drinking contaminated water and accidentally inhaling some in the lungs (aspiration) and working in soil containing the bacteria.

• A milder infection (which does not infect the lungs - no pneumonia) can be caused by the legionella bacteria called Pontiac fever. Symptoms include fever, chills, muscle aches, and headache, lasts about 2-5 days, and go away without treatment.

• Outbreaks of Legionnaires’ disease can be prevented with meticulous cleaning of the source.

Sources Used



Photo Credit

Image courtesy of the Centers for Disease Control and Prevention.