Those of us who were alive back in 1976 probably remember hearing about a mysterious disease that afflicted approximately 220 individuals who attended an American Legion convention in Philadelphia in July of that year. Sadly, 35 people succumbed to this "new" disease. The magnitude of the outbreak prompted an immediate investigation by the US Centers for Disease Control (CDC), who ultimately solved the mystery and gave the disease the name "Legionnaire's Disease".
Legionnaire's Disease is quite simply a type of pneumonia. Let's review the disease called "pneumonia" in order to understand Legionnaire's and put it in context. For starters, pneumonia is another name for a lung infection or inflammation. There are many different types of pneumonia and at least 30 different causes, including various strains of bacteria, viruses, fungi, mycoplasms, and even certain chemicals. Pneumonia symptoms run the gamut from mild to severe and most often include fever, cough, chills, and difficulty breathing.
The bacterium Legionella pneumophilia (abbreviated L. pneumophilia) causes Legionnaire's Disease. It enters the body when mist, steam, aerosols, or droplets which contain this bacterium are inhaled or aspirated into the lungs. Legionnaire's is an atypical, opportunistic form of pneumonia. It is atypical in that some of the symptoms (muscle aches, for example) aren't normally seen in other types of pneumonia. The fact that individuals with compromised immune symptoms (smokers, people with lung or other diseases, older individuals, etc.) are more susceptible to this disease makes it opportunistic.
Legionnaire's is not communicable and most people who are exposed to L. pneumophilia do not become sick. Unfortunately, those that do become ill may require hospitalization, as symptoms can be severe and Legionnaire's mortality rates are in the 5-30% range. Of the 8,000 to 18,000 annual US cases, about 20% are acquired when individuals travel outside of the country.
L. pneumophilia is a common contaminant in bodies of water. High concentrations of this organism in water increase your risk of infection and potential subsequent illness. L. pneumophilia quickly proliferates in stagnant water in the 68-122 degree (F) temperature range. It's easy to understand that the human body (98.6 degrees) is a near-perfect host for this organism. The same is true for any water system (residential hot water systems, cooling towers, hot water tanks, hot tubs, etc.) that operates in the 68-122 degree range.
While L.pneumophilia can exist in water as free-swimming bacteria, it often lives inside amoeba and other microscopic organisms that are normally found in water supplies. In addition, it has also adapted to live in biofilm, which is an aggregate of microorganisms which secrete a matrix and adhere to surfaces (think water pipes and other internal surfaces in water systems). These traits help L. pneumophilia survive in water supplies and resist treatments aimed at eradicating it.
Reduce the risk of Legionnaire's Disease at work and at home. Treated water supplies should be monitored frequently in order to optimize the biocide concentrations and pH. This will help to discourage the growth of L. pneumophilia and the organisms that it resides in. Inspect water systems on a regular basis and look for stagnant water, biofilm, and other deposits. Remove side-arm and dead-leg piping configurations, if possible. Periodically flush the system or shock treat it.
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