Last reviewed: July 2020
Last updated: July  2019



History and exam

Key diagnostic factors

  • known acquaintance with Legionella
  • fever
  • headache
  • crackles/ronchi

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-contaminated ice
  • delivery by water birth
  • exposure to contaminated compost
  • exposure to rainwater

Diagnostic investigations

1st investigations to order

  • CBC
  • complete metabolic profile
  • CXR
  • urine antigen detection of Legionella pneumophila serogroup 1
  • sputum Gram stain
  • cultures
More 1st investigations to order

Investigations to consider

  • Legionella pneumophila serology
  • direct fluorescent antibody (DFA) assay
  • Legionella pneumophila polymerase chain reaction (PCR)
More investigations to consider

Treatment algorithm


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 reviewersVIEW ALL

Professor of Medicine

University of Pittsburgh




VLY declares that he has no competing interests.

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