The Basics About Legionnaires’ Disease And HVAC Systems
Legionnaires’ Disease is a pulmonary infection caused by any species of the Legionella bacteria. The vast majority of documented cases are due to L. pneumophila. This species thrives in warm water with an optimal temperature of 35-degrees Celsius. However, it can multiply rapidly as long as its environment is between 25 and 45-degrees Celsius.
Signs and Symptoms
Infected persons will begin to exhibit signs and symptoms soon after exposure to the bacteria. The typical time period is between 2 and 10 days. There have been a few cases when this reached as long as 20 days. For the general population, exposures carry a 5% risk of disease development. Nearly everyone who has this condition has reported having high fever. Chills and cough are other common symptoms. Half have dry cough while the other half produce sputum, some of which are mixed with blood. These could be accompanied by headaches, fatigue, chest pain, muscle pain, impaired cognition, vomiting and diarrhea.
Modes of Transmission
This disease cannot be transmitted by an infected person to anyone else so there should be no fear about getting close to patients. The bacteria can only wreak havoc if contaminated water is vaporized and inhaled. What usually happens is that warm water in evaporative condensers of HVAC systems and cooling towers get overrun by the bacteria. As this is heated up, the vapor goes through the vents and gets circulated via centralized air conditioning. It is for this reason that a lot of the outbreaks occurred in hotels and other large indoor structures.
The most famous outbreak happened in 1976 in Philadelphia, Pennsylvania. The American Legion held their convention at the Bellevue-Stratford Hotel. Participants suddenly got sick one-by-one and were rushed to the hospital. Thirty four of the 221 infected persons died from that single incident. The investigation panel traced the origins of the disease to the bacteria which circulated via central A/C. The species was named after this tragic convention. A lot of changes have been made to avoid a repeat of the outbreak including streamlined product designs, installation processes, and maintenance procedures.
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