Which clinical history is characteristic of Legionnaires disease?

Updated: Mar 11, 2021
  • Author: Chinelo N Animalu, MD, MPH; Chief Editor: Michael Stuart Bronze, MD  more...
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Answer

Legionella pneumophila causes 2 distinct disease entities. Legionnaires disease (LD) is characterized by pneumonia. Pontiac fever is a short-term, milder illness than LD and is not characterized by pneumonia, instead manifesting as fever and myalgias that resolve without treatment. Extra pulmonary legionellosis such as pericarditis, endocarditis and cellulitis although not common, has been reported in both immunocompromised and immunocompetent patients and can occur as isotated cases or in the setting of legionella pneumonia. Usually species other than L pneumophila have been implicated in these cases. [11, 12]

The incubation period in LD ranges from 2-10 days. Patients who develop legionellae infection and who have been hospitalized continuously for 10 or more days before the onset of illness are classified as having definite nosocomial LD. Patients with laboratory-confirmed infection that develops 2-9 days after hospitalization are classified as having possible nosocomial LD. Nosocomial LD occurs in clusters.


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