Why is Legionella bacteria in my water

Where does Legionella come from?
Legionella is a naturally occurring bacterium.  It is found in lakes, rivers, streams, deep water wells, and even salt water. Legionella bacteria have been isolated from soil and dirt; in short it is all around us every day.  The bacteria’s natural habitat is within the biofilms and slime masses found on many wet surfaces.  One unique aspect of the Legionella bacteria is its ability to live and multiply inside an amoeba (Protozoa). Most bacteria, when absorbed by an amoeba are eaten; Legionella eats the amoeba and then emerges from the amoeba in far greater numbers.

Why is Legionella a problem in potable water?
Legionella bacteria can cause a range of respiratory illnesses in people often called legionellosis; best known is Legionnaires’ Disease a severe and often fatal pneumonia, a milder form of infection also reported is called Pontiac fever. The CDC estimates that every year 8,000-18,000 legionellosis cases occur in the U.S. However, accurate data reflecting the true incidence of disease are not available because of underutilization of diagnostic testing and under-reporting. The majority of reported cases are sporadic and many go unnoticed. Travel-associated outbreaks, hospital associated cases, outbreaks in community settings, and occupational outbreaks are common. All cases of legionellosis must be reported to the State Department of Health who will then inform the CDC.

Potable water systems have been reported as the source of up to 35 percent of all cases of Legionellosis, with even higher percentages of hotel and hospital related cases traced to the potable water system. The most common route of infection is through inhalation of a spray or mist containing the Legionella bacteria, though other routes of infection have been identified. One of the most common routes of aerosol production on a potable water system is the shower. The shower produces a fine mist of water that the user then stands directly within; any Legionella in the water will be directly in the breathing zone of the bather.

Not everyone who is exposed to Legionella becomes infected. Depending on the condition of your immune system, age, stress levels and other underlying health issues, you may not become infected. There are over 84 known species of Legionella bacteria, not all are equally infectious nor is the number of bacteria required to initiate infection fully known. However, we do know that in the absence of the bacteria, no infection will occur.

Why is Legionella in my potable water?
Because Legionella is present in nature whenever we extract water from lakes, rivers and even aquifers, we should anticipate that Legionella will enter the water treatment system. The water treatment process used to kill off other harmful bacteria does not always completely eliminate Legionella, allowing small amounts of the bacteria to enter the water distribution system and ultimately the plumbing system of your building. In some parts of the U.S. where ground water is used, there is no requirement to have any anti-bacterial treatment of the water, thus allowing trace amounts of Legionella to enter the water supply unimpeded. Even where the treatment works can completely remove the Legionella, leaks in distribution pipe-work, pipe breaks and similar interruptions can result in bacteria from soil and dirt entering the city water supply.

Once Legionella enters the plumbing system, it has the opportunity to grow and multiply provided the conditions are right.  The right conditions are typically based on temperature and nutrient levels. The ideal temperature for Legionella to grow is between 68 and 122oF; any higher temperature and the bacteria can be killed, any lower and it becomes dormant.  But at the right temperature, Legionella will happily grow in your plumbing system, emerging from the shower head or faucet to place your guests at risk of infection. The problem is exacerbated in many institutions such as assisted living facilities where Code mandates a hot water temperature of 110 to 115oF, ideal for growing Legionella.  One study by Hodgson and Casey that looked at over 5000 samples from well-maintained systems showed that Legionella is more likely to be present in a potable water system (7 percent) than in a cooling tower (6 percent).  Here are some effects at typical temperature levels:





Can AquaMedix filters remove other bacteria?
The microfilter in our Legionella filters removes 99.99999% of particulate of greater than 0.20 micron in size. The majority of bacteria exceed 0.20 micron in their smallest aspect and hence are trapped in the filter and do not leave the plumbing system. Though bacteria can deform and change size somewhat, there is a limit to their ability to reduce in diameter. AquaMedix has test data demonstrating that the filter will provide a seven log reduction in concentration of Legionella and Pseudomonas. These two key bacteria are also good surrogates for a number of other gram negative rods that are commonly found in potable water systems such as Serratia, coliforms and Klebsiella.

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