Legionellosis: Causes

Pathogenesis (development of disease)

When Legionella bacteria – predominantly the bacterium Legionella pneumophila – are ingested via inhalation (of water – as an aerosol) or, in rarer cases, via aspiration, they bind to host cells in the lungs. The body’s immune system tries to eliminate the bacteria with the help of macrophages. However, this is not successful with all bacteria, resulting in the onset of disease symptoms, especially in immunocompromised individuals.

Etiology (causes)

Biographic causes

  • Newborns or children who are immunosuppressed.
  • Recent (up to 2 weeks) hospitalization.

Behavioral causes

  • Consumption of stimulants
    • Alcohol
    • Tobacco (smoking)

Causes related to disease

  • Chronic lung disease, unspecified
  • HIV infection

Medication

  • Immunosuppression
  • Glucocorticoid therapy
  • Tumor necrosis factor alpha antagonists

Other causes

  • Surgical interventions
  • Organ transplantation