Last reviewed: 2 Sep 2023
Last updated: 15 Sep 2023
Summary
Definition
History and exam
Key diagnostic factors
- known acquaintance with Legionella
- fever
- headache
- crackles/rhonchi
More key diagnostic factors
Other diagnostic factors
- productive cough
- dyspnea
- nausea/vomiting
- abdominal pain
- hypoxia
- tachycardia
Other diagnostic factors
Risk factors
- non-municipal water supply
- recent residential plumbing repair
- smoking
- cytotoxic chemotherapy
- corticosteroids
- electric water heater
- working >40 hours per week
- recent travel
- diabetes mellitus
- professional driver
- use of whirlpool spas
- living close to a cooling tower
- filling nebulizer, humidifiers, ventilator tubing, or lavage equipment with tap water
- close proximity to a decorative fountain
- consumption of Legionella pneumophila-contaminated ice
- delivery by water birth
- exposure to contaminated compost
- exposure to rainwater
More risk factors
Diagnostic investigations
1st investigations to order
- CBC
- complete metabolic profile
- chest x-ray
- urine antigen detection of Legionella pneumophila serogroup 1
- sputum Gram stain
- cultures
More 1st investigations to order
Investigations to consider
- Legionella pneumophila polymerase chain reaction (PCR)
- Legionella pneumophila serology
More investigations to consider
Treatment algorithm
ACUTE
mild/moderate Legionella pneumonia
severe Legionella pneumonia or no response to initial therapy
Contributors
Authors
Forest W. Arnold, DO, MSc, FIDSA

Professor of Medicine
Division of Infectious Diseases
Department of Medicine
School of Medicine
University of Louisville
Louisville
KY
Disclosures
FWA declares that he has no competing interests.
Acknowledgements
Dr Forest W. Arnold would like to gratefully acknowledge Dr Allen Griffin, a previous contributor to this topic.
Disclosures
AG declares that he has no competing interests.
Peer reviewers
Victor L. Yu, MD
Professor of Medicine
University of Pittsburgh
Pittsburgh
PA
Disclosures
VLY declares that he has no competing interests.
Differentials
- Coronavirus disease 2019 (COVID-19)
- Bacterial pneumonia
- Hospital-acquired pneumonia
More DifferentialsGuidelines
- Pneumonia in adults: diagnosis and management
- Infectious Diseases Society of America/American Thoracic Society consensus guidelines on the management of community-acquired pneumonia in adults
More GuidelinesCalculators
Community-acquired pneumonia severity index (PSI) for adults
CURB-65 pneumonia severity score
More CalculatorsLog in or subscribe to access all of BMJ Best Practice
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