Trends in legionnaires disease, 1980-1998: Declining mortality and new patterns of diagnosis

Abstract

New diagnostic tests and empirical therapy for pneumonia may have important ramifications for the identification, treatment, and control of legionnaires disease (LD). To determine trends in the epidemiology of LD, we analyzed data for 1980-1998 from the passive surveillance system of the Centers for Disease Control and Prevention. During this time period, there were 6757 confirmed cases of LD (median annual number, 360 cases/year). Diagnosis by culture and by direct fluorescent antibody and serologic testing decreased significantly; diagnosis by urine antigen testing increased from 0% to 69%. The frequency of isolates other than Legionella pneumophila serogroup 1 (LP1) decreased from 38% to 4% (P = .003). The case-fatality rate decreased significantly, from 34% to 12% (P