Last reviewed: 28 Sep 2021
Last updated: 27 Jul 2021



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
  • 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 investigations

1st investigations to order

  • CBC
  • complete metabolic profile
  • chest x-ray
  • urine antigen detection of Legionella pneumophila serogroup 1
  • sputum Gram stain
  • cultures

Investigations to consider

  • Legionella pneumophila serology
  • direct fluorescent antibody (DFA) assay
  • Legionella pneumophila polymerase chain reaction (PCR)

Treatment algorithm



Forest W. Arnold, DO, MSc, FIDSA
Forest W. Arnold

Associate Professor of Medicine

Division of Infectious Diseases

Department of Medicine

School of Medicine

University of Louisville




FWA declares that he has no competing interests.


Dr Forest W. Arnold would like to gratefully acknowledge Dr Allen Griffin, a previous contributor to this topic. AG declares that he has no competing interests.

Peer reviewers

Victor L. Yu, MD

Professor of Medicine

University of Pittsburgh




VLY declares that he has no competing interests.

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