Legionellosis presents with a flu-like illness with fever, myalgia, headache and nonproductive cough. Abdominal pain and diarrhea are common. Respiratory failure may occur in severe cases. The case-fatality rate is about 15%. People become infected by inhaling mists from contaminated water.
CASES/YEAR
53,000 (US); 533,000 (Global)
OTHER NAMES
Legionnaire disease; Legionella pneumophilia infection;
INCUBATION
2-10 days, usually 5-6 days; [CCDM]
INITIAL SYMPTOMS
Flu-like illness with fever, myalgia, headache and nonproductive cough; Abdominal pain and diarrhea are common. [CCDM]
PRECAUTIONS
Standard; "Not transmitted from person to person." [CDC 2007 Guideline for Isolation Precautions]
COMMENTS
FINDINGS:
Respiratory failure may occur in severe cases. The case-fatality rate is about 15%. [CCDM, p. 334] In about 50% of patients, the cough produces phlegm. Occasional findings are hemoptysis, confusion, and seizures. Myoglobinuria (positive urine dipstick for heme pigments) is relatively common. Rare cases of myocarditis and pericarditis; Splenomegaly is uncommon. Present in some cases are leukopenia, thrombocytopenia, DIC, and pyuria. No rash in this disease; Extrapulmonary dissemination may occur in immunocompromised patients. Cavitation of consolidated lung occurs in about 10% of immunosuppressed patients. Rarely seen are pleural effusions, pericarditis, and myocarditis. [PPID, p. 2813-4]
EPIDEMIOLOGY:
People become infected by inhaling mists from contaminated water, e.g., cooling towers, humidifiers, whirlpool spas, showers, and decorative fountains. [CCDM, p. 335] Setting for Legionellosis: 1.) Stagnant water; 2.) Water is warm (77-108 deg F.); 3.) Water is aerosolized; Legionellosis: <5% of people exposed to source of outbreak develop disease; Pontiac fever: up to 95% of people exposed develop the disease. [CDC Travel, p. 257-8] Uncommon as a cause of pneumonia in children; [PPID, p. 2811]
RELATED DISEASE:
Pontiac fever is not an infection, but a form of inhalation fever caused by exposure to mists contaminated with Legionella pneumophilia. Patients have self-limited flu-like symptoms within 72 hours of exposure, and do not develop pneumonia. [CDC Travel, p. 258] The incubation period is usually 24-48 hours. [CCDM]
DIAGNOSTIC
Sputum culture; difficult & requires >3 days of growth; Urinary Ag assay: specific & fast, but only for L. pneumophilia serogroup 1 (causes 70% of cases); [ABX Guide] If Pontiac fever, cannot isolate organism. [CDC Travel]
SIGNS & SYMPTOMS
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>fatigue, weakness
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>fever
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>fever, biphasic or relapsing
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>myalgia
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>relative bradycardia
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G abdominal pain
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G diarrhea
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G liver function test, abnormal
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G nausea, vomiting
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H hemolysis
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H leukocytosis
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H leukopenia
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H splenomegaly
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H thrombocytopenia
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N confusion, delirium
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N headache
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N seizure
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R chest pain
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R cough
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R dyspnea
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R hemoptysis
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R sputum production
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U hematuria
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U pyuria
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X cystic or cavitary lesions
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X lung infiltrates
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X pleural effusions
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*acute renal failure
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*ARDS
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*arthritis
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*bleeding tendency
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*encephalitis
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*endocarditis
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*glomerulonephritis
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*myocarditis
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*pancreatitis
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*pericarditis
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*pneumonia
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*rhabdomyolysis
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*shock
SOURCE
Waterborne (Ingesting, Inhaling, or Swimming)
RISK FACTORS
- Cancer patients
- Inhale bioaerosols indoors
- Inhale mists of contaminated water from plastics injection molding
- Victim--air release of infectious agents
- Work in a medical or research lab
REFERENCES FOR CASES/YEAR
1. (US) MMWR 2011: 4,202; About 5000 cases per year reported in the US; [Cecil, p. 1963] 4200 cases reported in 2011 (13.5/million); 22.4/million reported in France in 2007; Community-based study in Ohio found an estimated 8,000 to 18,000 cases per year in the US (hospitalized for pneumonia); Another study estimated 40-280/million outpatient cases; Thus, best estimate of 18,000 to 88,000 annual cases in the US; [PPID, p. 2811] Ranked 4th in CAP behind S. pneumoniae, H. influenzae, and C. pneumoniae; [Harrison ID, p. 495] Calculate (18,000 + 88,000)/2 = 53,000 cases/year;
2. (Global) Occurs predominately in industrialized countries in which standing water is aerosolized by man-made devices; [Cecil, p. 1963] Guesstimate: Assume 1/2 of world population industrialized with same rate as US; Calculate: 10 X 53,000 = 530,000;