Legionnaires• Disease: Clinical Differentiation from Typical And
Legionnaires’ Disease: Clinical Differentiation from Typical and Other Atypical Pneumonias a,b, Burke A. Cunha, MD, MACP * KEYWORDS Clinical syndromic diagnosis Relative bradycardia Ferritin levels Hypophosphatemia HISTORY An outbreak of a severe respiratory illness occurred in Washington, DC, in 1965 and another in Pontiac, Michigan, in 1968. Despite extensive investigations following these outbreaks, no explanation or causative organism was found. In July 1976 in Philadel- phia, Pennsylvania, an outbreak of a severe respiratory illness occurred at an Amer- ican Legion convention. The US Centers for Disease Control and Prevention (CDC) conducted an extensive epidemiologic and microbiologic investigation to determine the cause of the outbreak. Dr Ernest Campbell of Bloomsburg, Pennsylvania, was the first to recognize the relationship between the American Legion convention in 3 of his patients who attended the convention and who had a similar febrile respiratory infection. Six months after the onset of the outbreak, a gram-negative organism was isolated from autopsied lung tissue. Dr McDade, using culture media used for rickettsial organisms, isolated the gram-negative organism later called Legionella. The isolate was believed to be the causative agent of the respiratory infection because antibodies to Legionella were detected in infected survivors. Subsequently, CDC investigators realized the antecedent outbreaks of febrile illness in Philadelphia and in Pontiac were caused by the same organism. They later demonstrated increased Legionella titers in survivors’ stored sera. The same organism was responsible for the pneumonias that occurred after the American Legionnaires’ Convention in Philadelphia in 1976. a Infectious Disease Division, Winthrop-University Hospital, 259 First Street, Mineola, Long Island, NY 11501, USA b State University of New York School of Medicine, Stony Brook, NY, USA * Infectious Disease Division, Winthrop-University Hospital, 259 First Street, Mineola, Long Island, NY 11501.
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