Legionnaires' disease review

This topic was recently reviewed in Lancet.

From the summary and introduction:

Since first identified in early 1977, bacteria of the genus Legionella are recognised as a common cause of community-acquired pneumonia and a rare cause of hospital-acquired pneumonia. Legionella bacteria multisystem manifestations mainly affect susceptible patients as a result of age, underlying debilitating conditions, or immunosuppression. Water is the major natural reservoir for Legionella , and the pathogen is found in many different natural and artificial aquatic environments such as cooling towers or water systems in buildings, including hospitals. The term given to the severe pneumonia and systemic infection caused by Legionella bacteria is Legionnaires' disease...

Bacteria of the genus Legionella were discovered during the investigation of a major pneumonia outbreak in members of the American Legion attending their annual meeting in 1976 in Philadelphia. 1 The causative microorganism was an unknown bacterium and was designated Legionella pneumophila . The term given to the infection was Legionnaires' disease, which refers to the pneumonic form of legionellosis. 29 (16%) of 182 patients died, and this new type of pneumonia did not respond to β-lactam antibiotics...

Macrolides, doxycycline, and quinolones are the main effective antibiotics...

According to the review LD is under diagnosed and under reported. In contrast to pneumococcal pneumonia the pathogenesis is inhalation rather than aspiration. The urine antigen is the first line test though there are limitations as described in the text.