Summary
Definition
History and exam
Key diagnostic factors
- known acquaintance with Legionella
- fever
- headache
- crackles/rhonchi
Other diagnostic factors
- productive cough
- dyspnea
- nausea/vomiting
- abdominal pain
- hypoxia
- tachycardia
Risk factors
- non-municipal water supply
- recent residential plumbing repair
- smoking
- cytotoxic chemotherapy
- lung transplant recipient
- 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
Diagnostic tests
1st tests to order
- CBC
- complete metabolic profile
- chest x-ray
- CT abdomen
- urine antigen detection of Legionella pneumophila serogroup 1
- sputum Gram stain
- cultures
Tests to consider
- Legionella pneumophila polymerase chain reaction (PCR)
- Legionella pneumophila serology
Treatment algorithm
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 has received grants from the National Institutes of Health, Health Resources and Services Administration, as well as Pfizer, Covarsa, Merck, and Gilead pharmaceutical companies.
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.
Peer reviewer acknowledgements
BMJ Best Practice topics are updated on a rolling basis in line with developments in evidence and guidance. The peer reviewers listed here have reviewed the content at least once during the history of the topic.
Disclosures
Peer reviewer affiliations and disclosures pertain to the time of the review.
References
Key articles
Phin N, Parry-Ford F, Harrison T, et al. Epidemiology and clinical management of Legionnaires' disease. Lancet Infect Dis. 2014 Oct;14(10):1011-21.Full text Abstract
Centers for Disease Control and Prevention. CDC Yellow Book 2024: health information for international travel. Section 5: travel-associated infections & diseases (bacterial) - legionnaires' disease & pontiac fever. May 2023 [internet publication].Full text
US Centers for Disease Control and Prevention. Legionella (Legionnaires' disease and pontiac fever): diagnosis, treatment, & prevention. March 2021 [internet publication].Full text
Metlay JP, Waterer GW, Long AC, et al. Diagnosis and treatment of adults with community-acquired pneumonia. An official clinical practice guideline of the American Thoracic Society and Infectious Diseases Society of America. Am J Respir Crit Care Med. 2019 Oct 1;200(7):e45-67.Full text Abstract
Reference articles
A full list of sources referenced in this topic is available to users with access to all of BMJ Best Practice.
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 Calculators
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