Legionnaire's Disease Since Philadelphia: Lessons Learned and Continued Progress.

Legionnaire's disease has been recognized as a cause of severe community-acquired pneumonia (CAP). Legionnaire's disease has characteristic extrapulmonary findings that are the basis for a presumptive clinical diagnosis. The widespread use of Legionella culture, sputum DFA, serology, urinary antigen testing, and polymerase chain reaction have allowed earlier diagnosis of Legionnaire's disease. Excluding common source outbreaks, CAP caused by Legionnaire's disease is manifested as sporadic cases. In contrast, nosocomial Legionnaire's disease occurs in clusters or outbreaks from common Legionella species-contaminated water sources. Improved diagnostic tests have permitted accurate diagnosis. Bacterial coinfections with Legionnaire's disease are uncommon, but when present, are most often associated with bacteremia pneumococcal pneumonia.