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Legionnaire’s Disease and Pontiac Fever

If you need assistance with legionnaire’s disease as discussed in this article call us at 1-800-344-4414 or email us at info@atlenv.com for details and a free estimate.

Written by Robert E. Sheriff, MS, CIH, CSP, President and Henry P. Shotwell, Ph.D., CIH, Vice-President

November 9, 2018, Updated April 2019

Legionnaire’s Disease Caused by Legionella Pneumophila

Legionnaire’s Disease is an environmentally transmitted disease caused by the Legionella Pneumophila bacteria that infect human hosts who breathe minute droplets of water that have been contaminated with the Legionella organism, a gram-negative bacterium.

Legionella Pneumophila – the legionnaire’s disease bacteria thrives in water temperatures between 95 and 115 degrees Fahrenheit. Its growth is inhibited at temperatures outside this range.

In residences, the most common sources of Legionella microorganisms are aerosolized water from sink traps and shower heads with the actual source being the hot water heater or old hot water piping. In commercial buildings, medical buildings and healthcare institutions, the most likely sources are hot water and cooling towers. In medical facilities, it is not unusual to set the hot water temperature low (100-120°F) to prevent burns, but this creates a possible growth environment for the Legionella bacteria. Cooling towers receive warm or hot water and cool it, but the warm water can be an incubator for Legionella Pneumophila if not properly treated. In other cases, hot tubs—and saunas—that were not properly treated with a bactericide have been sources of Legionnaire’s Disease and Pontiac Fever since the water temperature seems to be in the 100-120°F range.

Legionella is ubiquitous. It is likely to be found in every water system to some degree. But just because Legionella is present, it doesn’t mean infection will occur. Sometimes, people who are hospitalized with respiratory problems are tested for Legionella antibodies and show a positive test. This doesn’t necessarily mean the patient has a case of Legionnaire’s Disease. Most people have developed antibodies to Legionella without ever becoming infected. The truth is the most people who live in a mega-metropolitan area have been subjected to Legionella (such as NYC) have developed antibodies for the bacteria.

Legionnaire’s Disease History

Legionnaire’s Disease first came to our attention in July 1976, when 240 attendees at an American Legion Convention in Philadelphia were struck by an unrecognized respiratory disease that claimed 34 lives. After many months’ investigation, the causative agent, a previously unknown bacterium, Legionella pneumophila, was identified. Today, there are 48 known species of Legionella. A milder form of this infection is called Pontiac Fever named for a 1968 outbreak in Pontiac, Michigan. Both Legionnaire’s and Pontiac Fever are caused by the same Legionella pneumophila bacterium, but patients with Pontiac Fever do not have pneumonia, unlike those with Legionnaire’s Disease.


The best way to minimize the possibility of a Legionella outbreak is through proper maintenance of the water system, especially the hot water systems and cooling towers. This includes identifying and removing “dead legs” in the piping which contains stagnant water; removal of scale, sediment and biofilm, controlling temperatures in the system and regular treatments with biocides. Consulting a local water treatment lab can provide you with a list of biocides that will be effective in controlling Legionella and at the same time minimize corrosion to the system’s tanks and piping. Sending them a water sample can determine if the bacteria is present.


The only way to know for sure if your facility’s water system is harboring potentially harmful levels of Legionella is to test the water. The USEPA approved procedure is to take two samples from a faucet; one is a “first catch,” collected when the hot water faucet is turned on. The second sample is collected after the hot water has been allowed to run long enough for the water leaving the faucet is as hot as it will get. These samples and the Legionella organism are fragile and must be in the hands of the lab not more than 24 hours after collection. Ridding a system of Legionella Bacteria is a difficult task since they are ubiquitous (osha.gov/dts/osta/otm/legionnaires/index.html). If you rid the system of Legionella Bacteria but don’t eliminate the environment for their growth, they will return.

Identify and Eliminate the Source

Once someone has been diagnosed with Legionnaire’s Disease, especially in multi-family housing, commercial building, or healthcare facility, the local health department must be contacted. Thereafter, the efforts to identify the source and eliminate the source—and causes—will require the assistance of qualified professionals and likely involve the local health department.

For more information on Legionnaire’s Disease and Pontiac Fever, testing, identification, and elimination services contact Atlantic Environmental today. Use our contact form or call us at 800-344-4414 to discuss your Legionnaire and Pontiac Fever concerns and obtain a complimentary, no obligation quotation. We provide environmental consulting services tailored to your company’s requirements.

Our primary service areas for Legionnaire’s Disease Testing/Sampling and Consulting are: NJ, NY, NYC, PA, CT, DE, (Boston) MA, RI, Wash DC, WI, MD, MI, (Chicago) IL, VA, IN, (Atlanta) GA, AL, NC, SC, TN, (Dallas, Ft Worth) TX, OK, DC, AR, we can service most other areas of the U.S. but with some added travel charges.

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