by | General Liability |

What is Legionnaires’ Disease?

The Centers for Disease Control and Prevention (the CDC) states that each year between 8,000 and 18,000 people are hospitalized with Legionnaires’ disease in theU.S.  Legionnaires’ disease is a potentially deadly, infectious disease caused by gram-negative bacteria (legionella), and is a form of lung infection which produces high fever and pneumonia.  The disease occurs whenever someone breathes in a mist of vapor that has been contaminated with the bacteria.

The bacteria is found throughout nature.  However, the conditions are rarely favorable for people to catch the disease.  In addition, Legionnaires’ disease cannot be passed from human to human.   A person may contract the disease if exposed to the bacteria growing in systems where water temperatures encourage its proliferation.

The Ideal Environment

The bacterium’s ideal growing environment is warm, freshwater between 68° F-122° F.    Hot water heaters, cooling towers, air conditioners, and spa pools are all examples of places where the bacteria may gather.

Hot Water Heaters

Hot water heaters can be an ideal spot for legionella to grow.  Many hot water heaters’ temperatures are kept at 120° F, which is the prime temperature for growth. To prevent the growth of legionella, you should keep your water heater’s temperature at 140F. At that temperature though, the water can scald human skin, or cause first degree burns. At a temperature of 140° F, it takes only three seconds to sustain a first degree burn, whereas at a temperature of 120° F, it takes eight minutes to produce first degree burns.  Therefore, the best solution is to keep the temperature of the water at 140° F to prevent legionella growth and to install a scald-guard so that the water at the tap only comes out at a maximum of 120° F.


Spas are also a popular place where legionella can be found. Spa temperatures should be kept at 105° F or below.  As noted, higher temperatures create a prime environment for the development of legionella. To properly protect your hot tub, the right disinfectant and pH levels are essential.  Test strips should be purchased to check water for adequate chlorine or bromine and pH levels.  Spas that are not kept clean and disinfected are at a much higher risk to carry the bacteria.  According to the CDC, spas should be disinfected and pH levels should be checked twice per day (or more if the spa has a lot of traffic).  The water should also be changed routinely.

Air Conditioners

Air conditioners most susceptible to the legionella bacteria are those with cooling towers.  Here’s how you can prevent cooling towers from spreading this disease:

  1. Eliminate the spray or minuscule droplets by employing drift eliminators.
  1. Prevent legionella accumulation in the system by checking, cleaning, and maintaining the cooling towers according to the manufacturer’s recommendation.

Prevention is Key

Legionnaires’ disease is still a major problem throughout theUnited Statesand many people continue to develop the disease each year.  Preventing legionella growth is one of the keys to suppressing future outbreaks and for ensuring a healthy living environment for our families, employees, and customers.

For more information regarding Legionnaires’ disease and prevention tips, please visit the following sources:

And remember: don’t forget to subscribe to our blog!  Stay informed on risk management information, tips and advice from Acadia Insurance specialists that are relevant to your business!


Acadia is pleased to share this material for the benefit of its customers.  Please note, however, that nothing herein should be construed as either legal advice or the provision of professional consulting services.  This material is for informational purposes only, and while reasonable care has been utilized in compiling this information, no warranty or representation is made as to accuracy or completeness.  Recipients of this material must utilize their own individual professional judgment in implementing sound risk management practices and procedures.

Share this: