Legionnaire disease causes?

Ref: Page 1138: Harrison 20th edition* The bacterium L. pneumophila leads to legionnaire disease.* The most common form of transmission of Legionella is inhalation of contaminated aerosols produced in conjunction with water sprays, jets or mists.* It has 2 distinct clinical syndromes: Legionnaires disease, which most often manifests as severe pneumonia accompanied by multisystemic disease, and Pontiac fever, which is an acute, febrile, self-limited, viral-like illness