Legionellosis, also known as Legionnaires disease, is a type of Pneumonia caused by legionella bacteria. Legionella was discovered in 1976 during a convention at the American Legion in Philadelphia, thus the origination of its name.
Legionellosis has two distinct forms: legionnaires disease, which is the more severe form of the infection and associated with pneumonia, and Pontiac fever, which is milder and not associated with pneumonia. The most common initial symptoms for legionnaires disease and Pontiac fever are anorexia, myalgia, malaise, and headache, followed by fever (up to 102°F to 105°F), chills, and a nonproductive cough. Other symptoms may include abdominal pain and diarrhea. The case-fatality ratio for legionnaires disease is 5% to 30%, whereas cases of Pontiac fever usually recover in two to five days without treatment. Legionnaire’s disease usually cannot be distinguished from other forms of pneumonia and requires certain tests to confirm the diagnosis.
Legionella species are commonly found in the environment, usually in water, such as hot- and cold-water taps and showers, creeks, ponds, whirlpool spas, and cooling towers and evaporative condensers of large air-conditioning systems. Outbreaks of legionellosis have been linked to these sources, as well as to decorative fountains, humidifiers, respiratory therapy devices, and misters like the ones found in produce areas in the grocery stores. These bacteria are most likely to reproduce to high numbers in warm, stagnant water.
Legionella is not transmitted from person to person however, it may be transmitted when a person breathes in particles of water from an infected area or through aspiration.
To prevent Legionellosis:
Cooling towers should be drained when not in use and mechanically cleaned and maintained according to the manufacturer’s recommendations.
Tap water should not be used in respiratory therapy devices.
Whirlpool spas and decorative fountains should be maintained according to the manufacturer’s recommendations. Persons responsible for maintenance of these items should regularly review up-to-date maintenance protocols.
After outbreaks, vigilant monitoring of proven infection sources should be maintained.
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