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Clinical and epidemiological characteristics of Legionnaires' disease in Southern Sweden, a population-based study

Wikén, Christian ; Eliasson, Jenny ; Alanko Blomé, Marianne LU ; Fält, Rosmarie ; Resman, Fredrik LU ; Ljungquist, Oskar LU and Wasserstrom, Lisa LU orcid (2025) In Infectious Diseases 57(8). p.741-752
Abstract

BACKGROUND: The study aimed to describe all diagnosed cases of Legionnaire's disease (LD) in south Sweden, regarding incidence, patient characteristics, diagnostics, outcomes, and infection control investigations.

METHODS: This population-based retrospective study was conducted in Skåne, on patients with LD between 2011-2021. Inclusion criteria were positive polymerase chain reaction (PCR) for
L. pneumophila/
Legionella spp. or a positive urinary antigen test (UAT), combined with a clinical presentation consistent with
Legionella infection and radiological evidence of pulmonary infiltrates.

RESULTS: A total of 280 patients met the inclusion criteria, with a mean incidence of 2.00 per 100,000 person-years... (More)

BACKGROUND: The study aimed to describe all diagnosed cases of Legionnaire's disease (LD) in south Sweden, regarding incidence, patient characteristics, diagnostics, outcomes, and infection control investigations.

METHODS: This population-based retrospective study was conducted in Skåne, on patients with LD between 2011-2021. Inclusion criteria were positive polymerase chain reaction (PCR) for
L. pneumophila/
Legionella spp. or a positive urinary antigen test (UAT), combined with a clinical presentation consistent with
Legionella infection and radiological evidence of pulmonary infiltrates.

RESULTS: A total of 280 patients met the inclusion criteria, with a mean incidence of 2.00 per 100,000 person-years (95% CI: 1.23-2.78). Empiric treatment covering
Legionella was administered in 15% of cases. Mortality rates were 13%, 15% and 23% at 30-, 90- and 365 days, respectively. UAT was performed in 88% of patients, with a 66% positivity rate. Lower respiratory tract PCR was performed in 76% of patients with a 90% positivity rate. Bacterial culture was positive in 43% of cases. Out of these,
L. pneumophila serogroup 1 was most common (58%), though a significant proportion were serogroups 2-14 (30%), which are not generally detected by UAT. Genetic matches between environmental and patient strains were established in 5% of cases.

CONCLUSION: Legionnaires' disease in Skåne is an uncommon but clinically significant condition. Few patients received appropriate empiric antibiotic treatment. Reliance on UAT alone is insufficient for establishing diagnosis, and species-specific PCR, particularly from lower respiratory samples, enhances detection. Environmental investigations frequently identified
Legionella in suspected settings; however, a definitive source of infection was rarely established.

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author
; ; ; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Infectious Diseases
volume
57
issue
8
pages
741 - 752
publisher
Taylor & Francis
external identifiers
  • pmid:40192664
  • scopus:105002616471
ISSN
2374-4235
DOI
10.1080/23744235.2025.2476532
language
English
LU publication?
yes
id
a09dd2be-1f78-4e9e-ac84-dce5ead95ce2
date added to LUP
2025-04-18 14:09:50
date last changed
2025-10-18 20:43:46
@article{a09dd2be-1f78-4e9e-ac84-dce5ead95ce2,
  abstract     = {{<p>BACKGROUND: The study aimed to describe all diagnosed cases of Legionnaire's disease (LD) in south Sweden, regarding incidence, patient characteristics, diagnostics, outcomes, and infection control investigations.</p><p>METHODS: This population-based retrospective study was conducted in Skåne, on patients with LD between 2011-2021. Inclusion criteria were positive polymerase chain reaction (PCR) for<br>
 L. pneumophila/<br>
 Legionella spp. or a positive urinary antigen test (UAT), combined with a clinical presentation consistent with<br>
 Legionella infection and radiological evidence of pulmonary infiltrates.<br>
 </p><p>RESULTS: A total of 280 patients met the inclusion criteria, with a mean incidence of 2.00 per 100,000 person-years (95% CI: 1.23-2.78). Empiric treatment covering <br>
 Legionella was administered in 15% of cases. Mortality rates were 13%, 15% and 23% at 30-, 90- and 365 days, respectively. UAT was performed in 88% of patients, with a 66% positivity rate. Lower respiratory tract PCR was performed in 76% of patients with a 90% positivity rate. Bacterial culture was positive in 43% of cases. Out of these,<br>
 L. pneumophila serogroup 1 was most common (58%), though a significant proportion were serogroups 2-14 (30%), which are not generally detected by UAT. Genetic matches between environmental and patient strains were established in 5% of cases.<br>
 </p><p>CONCLUSION: Legionnaires' disease in Skåne is an uncommon but clinically significant condition. Few patients received appropriate empiric antibiotic treatment. Reliance on UAT alone is insufficient for establishing diagnosis, and species-specific PCR, particularly from lower respiratory samples, enhances detection. Environmental investigations frequently identified<br>
 Legionella in suspected settings; however, a definitive source of infection was rarely established.<br>
 </p>}},
  author       = {{Wikén, Christian and Eliasson, Jenny and Alanko Blomé, Marianne and Fält, Rosmarie and Resman, Fredrik and Ljungquist, Oskar and Wasserstrom, Lisa}},
  issn         = {{2374-4235}},
  language     = {{eng}},
  number       = {{8}},
  pages        = {{741--752}},
  publisher    = {{Taylor & Francis}},
  series       = {{Infectious Diseases}},
  title        = {{Clinical and epidemiological characteristics of Legionnaires' disease in Southern Sweden, a population-based study}},
  url          = {{http://dx.doi.org/10.1080/23744235.2025.2476532}},
  doi          = {{10.1080/23744235.2025.2476532}},
  volume       = {{57}},
  year         = {{2025}},
}