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<.001) for all cases, from 46% to 14% (P<.0001) for nosocomial cases, and from 26% to 10% (P=.05) for community-acquired cases. LD-related mortality has decreased dramatically. The decrease in culture-based diagnosis limits the recognition of non-LP1 disease and impairs outbreak investigation, because fewer Legionella isolates are provided for further examination.

Acute respiratory distress syndrome in patients with Legionella pneumonia

“…Considering most patients in this study had severe forms of Legionella pneumonia, mortality was considerably lower than previously reported (19,20). Over the past decade there has been a substantial decline in mortality from Legionella infections in the US (21). Early initiation of empirical antimicrobial coverage for atypical bacteria, as well as the recent developments in critical care medicine, including the standardized protocols for lung protective ventilation (22), sedation (23), weaning (24), early goal directed therapy in sepsis (25) and conservative strategy of fluid management in patients with acute lung injury (26) could explain the lower mortality in the observed patients.…”

Comparative assessment of virulence traits in Legionella spp.

“…At least 48 species of legionellae have been identified, of which five species have been designated Legionella-like amoebic pathogens (LLAPs) comprising 70 distinct serogroups with more than half of the species of legionellae implicated in disease (Abu Adeleke et al, 1996;Benson & Fields, 1998;Lo Presti et al, 1999, 2001. Legionella pneumophila accounts for the vast majority of cases in most of the world, with L. micdadei ranking distantly second (Benin et al, 2002;Joshi & Swanson, 1999). L. longbeachae and L. dumoffii ranked third and fourth, respectively, in the latest survey of Legionnaires' disease in the USA (Benin et al, 2002).…”

“…Legionella pneumophila accounts for the vast majority of cases in most of the world, with L. micdadei ranking distantly second (Benin et al, 2002;Joshi & Swanson, 1999). L. longbeachae and L. dumoffii ranked third and fourth, respectively, in the latest survey of Legionnaires' disease in the USA (Benin et al, 2002). In contrast to the incidence of L. pneumophila in the USA, L. longbeachae is the predominant species of Legionella responsible for Legionnaires' disease in many regions of Australia (Doyle et al, 1998).…”

Can we truly rely on the urinary antigen test for the diagnosis? Legionella case report

“…While the mortality rate among patients with community‐acquired legionellosis ranges from 16% to 30%, with or without treatment using inactive antibiotics such as beta‐lactam agents, it reduces to less than 10% in patients with community‐acquired LP treated with potent therapies 11, 12, 13, 14, 15. In many countries, such as Japan, USA, and UK, cases of legionellosis should be reported immediately to the public health department.…”