Aerobic small gram-negative bacillus.
Reservoir is water (aerosolization by cooling towers, spas, showerheads, etc.) Occurs in outbreaks. Person-to-person transmission not documented.
Risk factors include:
Pneumonia (Legionnaires disease)
Pontiac fever (self-limited febrile illness)
Extrapulmonary infections rare, but include endocarditis
Infectious Disease consultation is advised to assist in evaluation, management of patients and infection control measures.
The preferred diagnostic tests are culture of lower respiratory secretions (e.g. sputum, bronchoalveolar lavage) and urinary antigen test.
CDC. Legionella (Legionnaires' Disease and Pontiac Fever). March 25, 2021. https://www.cdc.gov/legionella/clinicians/disease-specifics.html