Legionnaires' Disease
Legionellosis is an infection caused by the genus of Gram negative bacteria Legionella, notably Legionella pneumophila At least 50 species and 70 serogroups have been identified. L. pneumophila, a ubiquitous aquatic organism that thrives in warm environments (25 to 45 °C with an optimum around 35 °C) causes over 90% of Legionnaires' disease cases
The disease has two distinct forms:
Legionnaires' disease is the name for the more severe form of infection which includes pneumonia
Pontiac fever is a milder respiratory illness without pneumonia caused by the same bacterium.