Abstract

This article describes the clinical differentiation of Legionnaires ‘ disease from typical and other atypical pneumonias, with reference to the history, microbiology, epidemiology, clinical presentation including radiologic manifestations, clinical extra pulmonary features, nonspecific laboratory findings, clinical syndromic diagnosis, and differential diagnosis, therapy, complications, and prognosis of the disease. Pneumonia caused by any Legionella species is termed Legionnaires ‘disease. The outbreak in Pontiac, Michigan, known as “Pontiac fever,” had an acute febrile illness but did not have pneumonia as in the Philadelphia outbreak. The isolation of Legionella was the first crucial step in understanding Legionnaires ‘disease. The initial isolation of Legionella pneumophila paved the way for ecological/epidemiologic studies, various direct and indirect diagnostic tests, and refining our therapeutic approach to Legionnaires ‘disease. Legionnaires' disease symptoms are similar to other types of pneumonia and it often looks the same on a chest x-ray. Legionnaires' disease can also be associated with other symptoms such as diarrhea, nausea, and confusion. Symptoms usually begin 2 to 14 days after being exposed to the bacteria, but it can take longer.