Legionellosis

Disease/Syndrome
Legionellosis
Category
Infection, Occupational
Acute/Chronic
Acute-Severe (life-threatening)
Synonyms
Legionnaires' disease; Legionella pneumophilia infection
Biomedical References
Comments
INITIAL SYMPTOMS:
Flu-like illness with fever, myalgia, headache and nonproductive cough; Abdominal pain and diarrhea are common. [CCDM]

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. 2639-40]

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. 224] Uncommon as a cause of pneumonia in children; [PPID, p. 2637]

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. 224] The incubation period is usually 24-48 hours. [CCDM]

For updated text and symptoms of infectious diseases, see iddx.com.
Latency/Incubation
2-10 days, usually 5-6 days; [CCDM]
Diagnostic
Sputum culture; difficult & requires >3 days of growth; Urinary Ag assay: specific & fast, but only for L. pneumophilia serogroup 1 (causes 70-80% of cases); [ABX Guide] Paired sera; "A single antibody titer of any level is not diagnostic" [CDC Travel]
ICD-9 Code
482.84
ICD-10 Code
A48.1; A48.2
Effective Antimicrobics
Yes

Symptoms/Findings, Job Tasks, and Agents Linked to This Disease

Agents

Hazardous agents that cause the occupational disease: