eMedicine Specialties > Emergency Medicine > Infectious Diseases

Legionnaires Disease

Author: Frank C Smeeks lll, MD, Chief Medical Officer, Frye Regional Medical Center
Contributor Information and Disclosures

Updated: Jun 1, 2009

Introduction

Background

An outbreak of serious pulmonary infections among people attending a convention of the American Legion in Philadelphia during the US Bicentennial celebration in July 1976 prompted the description of Legionnaires disease and its causative organism, Legionella pneumophila.

A nonpneumonic variant caused by the same species is called Pontiac fever, named for an outbreak of the described disease in Pontiac, Michigan, in 1968.

Pathophysiology

Legionella species are poorly staining, obligate, aerobic, gram-negative bacilli. Serogroup 1 is most frequently identified in clinical disease, but 18 serogroups of L pneumophila are presently known. Other than L pneumophila, 34 species of Legionella have been identified, mostly from immunocompromised patients with pneumonia.

Although pneumonia is the most common presenting problem, other pulmonary manifestations are frequent. The constitutional, cardiac, gastrointestinal, neurologic, renal, musculoskeletal, hepatic, and hematologic abnormalities variably seen with this disease are elaborated in Clinical.

This electron micrograph depicts an amoeba, <EM>H...

This electron micrograph depicts an amoeba, Hartmannella vermiformis (orange), as it entraps a Legionella pneumophila bacterium (green) with an extended pseudopod. After it is ingested, the Legionella pneumophila bacterium can survive as a symbiont within what then becomes its protozoan host. The amoeba then becomes what is referred to as a "Trojan horse," for by harboring the pathogenic bacteria, the amoeba can afford them protection, and in fact, in times of adverse environmental conditions, are able to metamorphose into a cystic-stage enabling it, and its symbiotic resident pathogens to withstand such environmental stresses. Image courtesy of the Centers for Disease Control and Prevention and Dr. Barry S Fields.

This electron micrograph depicts an amoeba, <EM>H...

This electron micrograph depicts an amoeba, Hartmannella vermiformis (orange), as it entraps a Legionella pneumophila bacterium (green) with an extended pseudopod. After it is ingested, the Legionella pneumophila bacterium can survive as a symbiont within what then becomes its protozoan host. The amoeba then becomes what is referred to as a "Trojan horse," for by harboring the pathogenic bacteria, the amoeba can afford them protection, and in fact, in times of adverse environmental conditions, are able to metamorphose into a cystic-stage enabling it, and its symbiotic resident pathogens to withstand such environmental stresses. Image courtesy of the Centers for Disease Control and Prevention and Dr. Barry S Fields.


Frequency

United States

Since the initial identification of 235 cases in 19761 , Legionnaires disease has become recognized as the most common cause of atypical pneumonia in hospitalized patients. It is the second most common cause of community-acquired bacterial pneumonia. Legionnaires disease is reportable in the United States. The Centers for Disease Control and Prevention (CDC) received reports of 1241 cases in 1995, indicating an incidence of 0.48 cases per 100,000 people.1 This represents passive disease surveillance. More active surveillance methods estimate that upwards of 20,000 cases occur annually in the United States. Prevalence reports of Legionella have increased with time likely due to the availability of more effective testing modalities. However, it is also possible that Legionella infections are increasing in frequency for environmental, population, or behavioral reasons. 

International

Outbreaks have been recognized throughout North America, Africa, Australia, Europe, and South America.

Mortality/Morbidity

  • Legionnaires disease has a 25% mortality rate. However, this figure should be interpreted cautiously because of possible underreporting of comorbid disease.
  • Legionnaires disease is frequently associated with gastrointestinal symptoms, including nausea, vomiting, diarrhea, and abdominal pain.
  • Neurologic symptoms are also common, including lethargy, altered mental status, and nonfocal neurologic examination findings.
  • Hyponatremia is common in Legionnaires disease.
  • Rhabdomyolysis and renal failure may be seen in this disease.

Sex

Men are affected more frequently than women.

Age

  • The weighted mean age for patients with Legionnaires disease is 52.7 years, with increasing incidence until age 79.
  • The incidence in persons younger than 35 years is less than 0.1 cases per 100,000 people.
  • Older patients have higher mortality rates.

Clinical

History

Legionnaires disease is more common in the summer, especially in August, and is slightly more prevalent in the northern US.
  • The classical presentation begins with an incubation period of 2-10 days.
  • Patients often experience a prodrome of 1-2 days of mild headache and myalgias, followed by high fever, chills, and multiple rigors.
  • Cough is present in 90% of cases; cough usually is nonproductive at first but may become productive as the disease progresses.
  • Other pulmonary manifestations include dyspnea, pleuritic chest pain, and hemoptysis, which may be present in as many as one third of cases.
  • Gastrointestinal symptoms include nausea, vomiting, diarrhea, and anorexia.
  • Neurologic symptoms include headache, lethargy, altered mental status, and rarely, focal symptoms.
  • Musculoskeletal symptoms include arthralgias and myalgias.
  • Nonpulmonary symptoms are prominent early in the disease.

Physical

  • The vital signs may reveal high fever and tachypnea. Relative bradycardia may occur in up to 66% of patients.
  • Absence of inflammation of the upper respiratory tract is common and is a clinically useful indicator.
  • Chest auscultation findings may be normal or may reveal rales, rhonchi, or signs of consolidation.
  • Pericarditis and endocarditis may be present.
  • Hepatomegaly may be seen in rare cases.
  • The neurologic examination findings or the patient's mental status may be abnormal.
  • The patient may have blood-streaked sputum.
  • Mild, generalized abdominal pain and bloating may be present.
  • The rest of the physical examination may be unremarkable, but signs and symptoms of risk factors for the disease should be sought.

Causes

  • Investigations of outbreaks have documented aerosol transmission from contaminated water sources, including the following (Note: No person-to-person spread of Legionella is documented.):
    • Cooling systems
    • Showers
    • Decorative fountains
    • Humidifiers
    • Respiratory therapy equipment
    • Whirlpool spas
  • Risk factors for Legionnaires disease include the following:
    • Smoking
    • Diabetes
    • Cancer, particularly hematological or pulmonary malignancy
    • AIDS
    • End-stage renal disease
    • Chronic cardiopulmonary disease
    • Advanced age
    • Alcohol abuse
    • Surgery

More on Legionnaires Disease

Overview: Legionnaires Disease
Differential Diagnoses & Workup: Legionnaires Disease
Treatment & Medication: Legionnaires Disease
Follow-up: Legionnaires Disease
Multimedia: Legionnaires Disease
References
Further Reading

References

  1. CDC. Summary of notifiable diseases, United States 1995. MMWR Morb Mortal Wkly Rep. Oct 25 1996;44(53):1-87. [Medline].

  2. [Guideline] Mandell LA, Wunderink RG, Anzueto A, Bartlett JG, Campbell GD, Dean NC, et al. Infectious Diseases Society of America/American Thoracic Society consensus guidelines on the management of community-acquired pneumonia in adults. Clin Infect Dis. Mar 1 2007;44 Suppl 2:S27-72. [Medline].

  3. Amsden GW. Treatment of Legionnaires' disease. Drugs. 2005;65(5):605-14. [Medline].

  4. Blanquer J, Blanquer R, Borras R, et al. Aetiology of community acquired pneumonia in Valencia, Spain: a multicentre prospective study. Thorax. Jul 1991;46(7):508-11. [Medline].

  5. CDC. Legionnaires disease associated with a whirlpool spa display--Virginia, September-October, 1996. MMWR Morb Mortal Wkly Rep. Jan 31 1997;46(4):83-6. [Medline].

  6. Cunna B. Legionnaire's disease - Case studies in infectious disease. Emerg Med. 1992;24:227-234.

  7. Falco V, Fernandez de Sevilla T, Alegre J, Ferrer A, Martinez Vazquez JM. Legionella pneumophila. A cause of severe community-acquired pneumonia. Chest. Oct 1991;100(4):1007-11. [Medline].

  8. Lane G, Ferrari A, Dreher HM. Legionnaire's disease: a current update. Medsurg Nurs. Dec 2004;13(6):409-14. [Medline].

  9. Marrie TJ, Haldane EV, Noble MA, Faulkner RS, Martin RS, Lee SH. Causes of atypical pneumonia: results of a 1-year prospective study. Can Med Assoc J. Nov 15 1981;125(10):1118-23. [Medline].

  10. Marston BJ, Lipman HB, Breiman RF. Surveillance for Legionnaires' disease. Risk factors for morbidity and mortality. Arch Intern Med. Nov 14 1994;154(21):2417-22. [Medline].

  11. Palmer L. Legionella pneumonia - Cardiopulmonary problems in the office. Emerg Med. 1992;24:84-94.

  12. Reingold AL. Role of legionellae in acute infections of the lower respiratory tract. Rev Infect Dis. Sep-Oct 1988;10(5):1018-28. [Medline].

  13. Shah A, Check F, Baskin S, Reyman T, Menard R. Legionnaires' disease and acute renal failure: case report and review. Clin Infect Dis. Jan 1992;14(1):204-7. [Medline].

Further Reading

Other resources

Legionellosis Resource Center


Clinical guidelines

Infectious Diseases Society of America/American Thoracic Society consensus guidelines on the management of community-acquired pneumonia in adults. Mandell LA, Wunderink RG, Anzueto A, Bartlett JG, Campbell GD, Dean NC, Dowell SF, File TM Jr, Musher DM, Niederman MS, Torres A, Whitney CG. Infectious Diseases Society of America/American Thoracic Society consensus guidelines on the management of community-acquired pneumonia in adults. Clin Infect Dis 2007 Mar 1;44 Suppl 2:S27-72. [335 references] PubMed

Keywords

Legionnaires disease, Legionnaires' disease, Legionella pneumophila, L pneumophila, atypical pneumonia, pulmonary infection, Pontiac fever, community-acquired bacterial pneumonia, CAP

Contributor Information and Disclosures

Author

Frank C Smeeks lll, MD, Chief Medical Officer, Frye Regional Medical Center
Frank C Smeeks lll, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Emergency Medicine, American College of Emergency Physicians, American College of Physician Executives, American Medical Association, and North Carolina Medical Society
Disclosure: Nothing to disclose.

Medical Editor

Eric M Kardon, MD, FACEP, Attending Emergency Physician, Georgia Emergency Medicine Specialists; Physician, Division of Emergency Medicine, Athens Regional Medical Center
Eric M Kardon, MD, FACEP is a member of the following medical societies: American College of Emergency Physicians
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: Nothing to disclose.

Managing Editor

Jeter (Jay) Pritchard Taylor III, MD, Compliance Officer, Attending Physician, Emergency Medicine Residency, Department of Emergency Medicine, Palmetto Health Richland, University of South Carolina; Medical Director, Department of Emergency Medicine, Palmetto Health Baptist
Jeter (Jay) Pritchard Taylor III, MD is a member of the following medical societies: American Academy of Emergency Medicine, American College of Emergency Physicians, American Medical Association, and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

CME Editor

John D Halamka, MD, MS, Associate Professor of Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center; Chief Information Officer, CareGroup Healthcare System and Harvard Medical School; Attending Physician, Division of Emergency Medicine, Beth Israel Deaconess Medical Center
John D Halamka, MD, MS is a member of the following medical societies: American College of Emergency Physicians, American Medical Informatics Association, Phi Beta Kappa, and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

Chief Editor

Rick Kulkarni, MD, Medical Director, Assistant Professor of Surgery, Section of Emergency Medicine, Yale-New Haven Hospital
Rick Kulkarni, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Emergency Medicine, American College of Emergency Physicians, American Medical Association, American Medical Informatics Association, Phi Beta Kappa, and Society for Academic Emergency Medicine
Disclosure: WebMD Salary Employment

 
 
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