Flu-like illness with fever, myalgia, headache and nonproductive cough; Abdominal pain and diarrhea are common. [CCDM]
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]
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]
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.
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]