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The Basics About Legionnaires’ Disease And HVAC Systems

September 18, 2015

Any person who is tasked with the responsibility of taking care of HVAC systems should know about Legionella pneumophila, the bacterium responsible for causing Legionnaires’ Disease. The recent outbreak of the disease has revealed just how little people know about the disease despite the fact that it was discovered decades ago.

The History of Legionnaires’ Disease

Legionnaires’ Disease is caused by L. pneumophila bacterium: the same type of microorganism that causes a milder form of Pontiac fever. The disease is a variation of pneumonia, so the symptoms are almost the same. The most common symptoms include; high fever, chills, coughing and aches among others. The first cases of the disease can be traced as far back as the 1960s. However, the disease and bacterium causing it were only named in 1976. This is after 221 participants of the American Legion Convention contracted the disease in Philadelphia. At the time, the origin and pathology of the disease were a mystery. Out of the 221 attendees who contracted the illness, 34 ended up dying, something that created national panic. This panic was partly fueled by government response to the outbreak, which is somewhat similar to the recent government warnings that there’s a possibility of a major outbreak.

What Causes an Outbreak of Legionnaires’ Disease?

L. pneumophila thrives in freestanding warm water, or warm stagnant water. This makes cooling towers in large HVAC systems the best habitat for the microorganism. It is spread to humans through inhalation of moist air that’s contaminated. This means that a large number of people who use a building with a contaminated HVAC system can quickly contract Legionnaires’ Disease. In fact, the 1976 outbreak at the American Legion Conference in Philly was blamed on the hotel’s poorly-maintained HVAC system.


While Legionnaires’ Disease is treatable, three out of every ten people who contract the disease die from it. According to the CDC, nearly 18,000 cases of the disease are reported every year. The key to dealing with the problem lies in regular servicing of HVAC systems according to industry best practices. Follow us for more articles that your HVAC systems running comfortable and efficiently.

About The Author

Brody Pennell

Since 1945, Brody Pennell Heating & Air Conditioning is the committed to helping homeowners in the greater Los Angeles area experience total home comfort. In 2021, the readers of the Los Angeles Times voted Brody Pennell the Best HVAC Company in the area.

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