Clinical Features of Legionnaires' Disease and Pontiac Fever

Key points

  • Legionnaires' disease and Pontiac fever are two illnesses caused by bacteria called Legionella.
  • Learn how they present differently in terms of clinical features, symptoms, and complications.
A healthcare provider listens to a man's breathing through a stethoscope

Clinical features

Legionnaires' disease

Legionnaires' disease is characterized by illness with pneumonia diagnosed radiographically or clinically.

Evidence of clinically compatible disease can be determined from the medical record in several ways:

  1. Clinical or radiographic diagnosis of pneumonia
  2. Description of clinical symptoms consistent with a pneumonia diagnosis

Pontiac fever

Pontiac fever is a milder, self-limiting illness without pneumoniaA.

Common signs and symptoms

Legionnaires' disease

Clinical symptoms may vary but include acute onset of lower respiratory illness with fever or coughA. Additional symptoms may be present:

  • Shortness of breath
  • Myalgia
  • Headache
  • Chest pain
  • Nausea, diarrhea, or abdominal pain
  • Altered mental status

Pontiac fever

Pontiac fever symptoms are mild and self-limiting, and can include:

  • Chills
  • Fatigue
  • Fever
  • Headaches
  • Malaise
  • Myalgia
  • Nausea or vomiting

Complications

Legionnaires' disease

Hospitalization is common. The case-fatality rate is approximately 10%. For healthcare-associated infections, the case-fatality rate averages 25%.

Pontiac fever

Hospitalization is uncommon. The case-fatality rate is extremely low.

Resources

Legionnaires' disease fact sheet for clinicians

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Content Source:
National Center for Immunization and Respiratory Diseases; National Center for Environmental Health
  1. According to the Council of State and Territorial Epidemiologists case definition.
  • Egan JR, Hall IM, Lemon DJ, Leach S. . Epidemiology. 2011;22(2):188–98.
  • Fraser DW, Tsai TR, Orenstein W, et al. . N Engl J Med. 1977;297(22):1189–97.
  • Glick TH, Gregg MB, Berman B, et al. . Am J Epidemiol. 1978;107(2):149–60.