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If you were to step onto the street and ask passers-by what they know about Legionnaires’ disease, you would be hard-pressed to find people with knowledge of the illness.  Surely, the majority would never have heard of it.  The truth is: Legionnaires’ disease, with its strange sounding name, is an underdiagnosed illness, thought to be less common than it actually is.  It is important to know why, as well as the implications of underdiagnosis.

An important reason why Legionnaires’ disease is underdiagnosed is that the set of symptoms accompanying it often match up better to more common illnesses.  The common symptoms of Legionnaires’ disease are: shortness of breath, productive cough, diarrhea, high fevers, weakness, body aches, headaches, nausea, and vomiting.  Many of these symptoms can be found in widespread illnesses such as: the common cold, the flu, food poisoning, and even more common types of pneumonia.  On the basis of symptoms alone, it is extremely difficult for physicians to diagnose Legionnaires’ disease specifically, which is one reason it is often overlooked.

Doctors are more inclined to consider a diagnosis for Legionnaires’ disease when they have been alerted of an outbreak and warned to be on the lookout for patients with a certain subset of symptoms who have been associated with an outbreak location.  Health departments warn medical providers and supply them with information on Legionnaires’ disease when an outbreak occurs in a specific region.  However, it takes time for Health Departments to discover outbreaks, and it is often a result of people getting sick, so the warning is too late in many cases.  In cases of Legionellosis, rarely is an epidemiological investigation—an investigation of various aspects of health conditions and diseases in populations–conducted prior to occurrences of the illness, solely on the basis of positive environmental samples from an outbreak location.  In fact, Health Departments generally do not investigate until after a cluster, or grouping of cases with a common source in a common timeframe, has been defined.  While there is no easy solution for this reactive approach, it means that doctors are often prompted to be wary of Legionnaires’ disease too late, and if an epidemiological investigation does not occur, they may never be alerted to look for Legionnaires’ disease.

Another factor influencing the underdiagnosis of Legionnaires’ disease is the relative difficulty of testing.  Several tests exist to determine if a patient has Legionnaires’ disease, including sputum, blood and urine antigen tests.  However, the timeframe of ordering and administering tests, as well as waiting for results is a limiting factor that certainly affects the rate at which these diagnostic tests are given.  Also, once patients begin a regimen of antibiotics, positive results are often masked, leading to further underdiagnosis of Legionnaires’ disease.

What are the implications of the underdiagnosis of Legionellosis?  Aside from the simple fact that people on the street are less likely to have heard of it, there are more serious consequences.  Physicians may choose a different course of treatment for patients with Legionnaires’ disease as opposed to other illnesses.  This can affect how well a patient recovers, the timeframe of recovery, and whether they recover at all.  From an epidemiological standpoint, health departments would likely greater prioritize Legionellosis if the numbers of diagnosed patients better reflected the number of people stricken with the illness.  This would mean stricter standards for maintaining water systems, perhaps greater emphasis on a need for environmental testing, and faster and more transparent systems of outbreak reporting.  Facilities where outbreaks commonly occur (such as hotels, hospitals and other locations with large public water supplies) would have more incentive to take proactive steps to prevent outbreaks if Legionnaires’ disease were viewed as a legitimate concern, one that is imminent without proper preparations.  Increased awareness in terms on the number of people afflicted by Legionellosis and the sources of their illnesses would generate greater emphasis on water maintenance and Legionella prevention.

The difficulty in this whole debate is obviously how to better diagnose Legionnaires’ disease.  We know that symptoms common to other illnesses, physicians’ reliance on health department notices, and issues with biological testing all create circumstances that prevent accurate diagnoses of Legionellosis.  And the impacts can be widespread.  But the real question is: how do we change, knowing that ultimately, improvements will save lives?



Posted by jzacher">jzacher at 3:23 pm

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