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Epidemiology Most L pneumophila infections are associated with water supplies and ventilation systems; most epidemics occur during the summer with 0.5–5% attack rates; the only documented mode of spead is aerosol
Sources Plumbing, shower heads, water-storage tanks, evaporative condensors, cooling towers
Risk factors Cigarettes, alcohol, renal transplant, elderly
DiffDx Sporadic LD mimics myoplasma pneumonia, Q fever, tularemia, plague, psittacosis, influenza and other viral pneumonias
Lab Decreased Na+, decreased PO4-, increased liver enzymes, proteinuria, microscopic hematuria, relative leukocytosis, increased ESR, hyponatremia, increased ALT, increased AST, increased BR, azotemia
Complications Empyema, shock, DIC, renal failure, neurologic sequelae, peripheral neuropathy
Management Erythromycin, T-S, penicillin
Prognosis 15–20% mortality w/o therapy; up to 50% of immunocompromised patients die
Poor prognostic features Tachycardia, tachypnea, WBCs 14,000/mm3, increased BUN, increased creatinine, hyponatremia, hypoxia, leukopenia, bilateral infiltrates on chest films
Prevention Chlorination of water supply for showers and ventilation systems; UV irradiation of water supplies
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.
legionnaires’ diseasea rare human pneumonial condition, caused by the bacterium Legionella pneumophila, that can lead to death. The disease was named after an outbreak occurring at an American Legion convention in a Philadelphia hotel in 1976, the bacteria eventually being traced to the air-conditioning plant of the hotel. Since then a number of cases have been reported in connection with recirculated hot water systems such as cooling towers. There is no evidence of person-to-person transmission.
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005