Legionnaires' Disease

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Legionnaires' disease

Legionnaires' disease


Legionnaires' disease (LD) is an acute bacterial pneumonia that results from infection with one or both Legionella bacteria: Legionella pneumophila and Legionella longbeachae. LD is usually self-limiting, but mortality rates have been 20-40n certain localized outbreaks and in hospital-acquired cases. Signs and symptoms of LD include malaise, dyspnea, chest pain, muscle aches, anorexia, headache, high fever, chills, hacking cough, and pneumonia, with occasional abdominal pain and diarrhea. (Roy, 2002)

LD is a waterborne disease but is not contracted by drinking contaminated water. Instead, LD is transmitted through inhalation of infectious particles from contaminated water (L. pneumophila) or less commonly, contaminated soil (L. longbeachae). Since its discovery in 1976, Legionella has been found to exist in the water supplies of large cities, small villages, and hospitals worldwide. Warm, simulated water environments (e.g., air-conditioning and cooling systems, water reservoirs of nebulizers and humidifiers, fountains, showers, spas) provide the best environment for growth of Legionella. There have been several large outbreaks of LD, but most cases are sporadic; person-to-person transmission does not occur. (Horwitz, 2003)


Legionella bacteria live in water or in soil soaked with water, and it must be inhaled or inhaled to cause infection. There is usually no line that removes bacteria from water, or soil for circulating the air, carried by tiny drops of water, while the cooling tower and modern evaporative condenser instead promote the passage of air in these waterborne bacteria. Most individuals who are exposed to Legionella will not develop LD, and milder cases of LD usually resolve without treatment. For this reason, many people carry antibodies to LD with no memory of infection. Older adults, cigarette smokers, and those who are immunocompromised (e.g., due to cancer or HIV/AIDS) and/or hospitalized prior to infection are at increased risk for severely symptomatic or fatal LD. LD is diagnosed by culture (e.g., of sputum, blood, or urine), urine testing for the Legionella antigen, and chest X-ray results of interstitial, patchy, or lobular pneumonia. In addition, when rapid diagnosis of LD diagnosis is necessary (e.g., during an H1N1 pandemic), diagnosis is also made by the presence of any 3 (called the diagnostic triad) of the following: lymphopenia mildly elevated hepatic transaminases, and increased ferritin levels or hypophosphatemia. Use of the diagnostic triad can rapidly diagnose LD in patients with community-associated pneumonia (CAP) who have extrapulmonary findings (e.g., diarrhea, mental confusion, headache, abdominal pain, bradycardia); (Hlady, 2003)

In buildings badly designed or poorly maintained, water spray and the vapor or tiny droplets can penetrate cracks in the ducts of air conditioning system, especially if they are located too close to the cooling tower. Water vapor, and droplets contaminated also come directly from the top of the cooler, and possibly win the cooling towers of neighboring buildings. Most of the time, Legionnaires' disease occurs in large institutions, especially in hotels and hospitals or cruise ships. The disease is spread through air conditioning systems, heating and cooling. Legionella can survive easily in hot water ...
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