Legionella causes two different manifestations of pulmonary disease: a mild, flulike illness, called Pontiac fever, and pneumonia. Pontiac fever has an incubation period of 1-2 days and is characterized by malaise, myalgias, fever, headache, and, sometimes, nonproductive cough. Only symptomatic therapy is required, and complete recovery within 1 week can be expected. Pneumonia, on the other hand, is the predominant manifestation of the more severe form of legionellosis, Legionnaires' disease. This pneumonia can be associated with multiorgan failure. The incubation period of legionnaires' disease ranges from 2 to 10 days, and antimicrobial chemotherapy is necessary for complete recovery of the patients. Nevertheless, in elderly or pulmonary-compromised patients, Legionnaires' disease has a mortality rate of up to 50%.[5,8]
Infection of humans mainly occurs through close contact with contaminated water sources, such as droplets and aerosols in spas, hot showers, and air-conditioning systems. Legionellae are responsible for 2-15% of community-acquired pneumonias, but the estimated number of infections is much higher. In addition, legion-ellae are a significant cause of nosocomial pneumonias, especially in immunocompromised and ICU patients.[5,8]
Nosocomial infections caused by legionellae are more often caused by L. pneumophila nonserogroup 1 and by legionellae other than L. pneumophila, corresponding to the epidemiology of the different Legionella species in water sources.
Was this article helpful?