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Legionnaires' disease - an atypical pneumonia

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Bernice Clark |
legionellaLegionnaires' disease is a severe form of pneumonia caused by a bacterium legionella pneumophila which lives in humid environment, in the cooling towers and big air conditioning systems like those in hospitals, hotels and malls.


Legionella bacterium natural environment is water and because of that it is often called "water bacterium". In spite of the name, the smaller number of the bacteria lives in natural water system like lakes, rivers, creeks and thermal springs. They rather colonize different water supply systems built by men (waterworks, reservoirs, ventilation system in large buildings, swimming pools, whirlpool spas, fountains...).

Temperature of 20-40C/68-104F, an organic and inorganic contamination, and water which stay in systems go in favour to legionella growing and multiplication. When the conditions in those systems become favourable for their reproduction, legionella multiplies so fast that aerosolized water droplets spread by air become infective for people when they inhale them.

A bacterium legionella pneumophila causes two different shapes of the disease: a severe form of pneumonia, which we call Legionnaires' disease and the Pontiac fever, a short lasting fever and the mild form of Legionnaires' disease which doesn't infects the lungs. Both illnesses are known by name legionellosis. However, while Pontiac fever usually clears on its own (some consider it as a hypersensitivity reaction to legionella bacteria, not the infection at all), untreated Legionnaires' disease can be fatal.

Legionnaires' disease starts as an atypical pneumonia, but it is much severe than other atypical pneumonia. The period from the infection to the first symptoms last 2 to 14 days causing pneumonia which can be fatal for 15-20 percent of infected people.

The first symptom of the disease is fever of 40C/104F or higher 41C/105.8. It is followed by chill, headache, pain in muscles and joints, nausea and general weakness. Two to five days later, the patient starts to cough. The symptoms look more like flu, and in its early stage the Legionnaires' disease can easily be mistaken with a range of other illnesses. But, as cough appears the patient has pain in chest, breathe shortness, fatigue, vomiting and diarrhea. Sometimes, the disease can attack liver and kidneys, even the nervous system causing confusion or other mental changes.

It is of utmost importance to visit doctor if you feel you catch flu, have fever 40C/104F or higher, muscle pain, headache, dry cough, pain in chest, shortness of breath, nausea, vomiting and diarrhea. If is not treated effectively and promptly with antibiotics, Legionnaires' disease may be fatal, especially if immune system is weakened by disease.

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