Legionellosis overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Legionellosis is an infectious disease caused by bacteria belonging to the genus Legionella.[1] Over 90% of legionellosis cases are caused by Legionella pneumophila, a ubiquitous aquatic organism that thrives in warm environments (25 to 45 °C with an optimum around 35 °C).[2]
Legionellosis takes two distinct forms:
- Legionnaires' disease is the more severe form of the infection and produces pneumonia.[3]
- Pontiac fever is caused by the same bacterium, but produces a milder respiratory illness without pneumonia which resembles acute influenza.[3]
Legionnaires' disease acquired its name in 1976 when an outbreak of pneumonia occurred among people attending a convention of the American Legion in Philadelphia. On January 18, 1977 the causative agent was identified as a previously unknown bacterium, subsequently named Legionella.
An estimated 8,000 to 18,000 people get legionellosis in the United States each year.[4] Some people can be infected with the Legionella bacterium and have only mild symptoms or no illness at all.
Outbreaks of Legionnaires' disease receive significant media attention. However, this disease usually occurs as a single, isolated case not associated with any recognized outbreak. When outbreaks do occur, they are usually recognized in the summer and early autumn, though cases may occur at any time of year. The fatality rate of Legionnaires' disease has ranged from 5 to 30% during various outbreaks.
References
- ↑ Ryan KJ, Ray CG (editors) (2004). Sherris Medical Microbiology (4th ed. ed.). McGraw Hill. ISBN 0838585299.
- ↑ CDC: Etiologic Agent
- ↑ 3.0 3.1 Winn WC Jr (1996). "Legionella". Baron's Medical Microbiology (Baron S et al, eds.) (4th ed. ed.). Univ of Texas Medical Branch. ISBN 0-9631172-1-1.
- ↑ CDC: Incidence