A community outbreak of Legionnaires’ disease in Geneva, Switzerland, June to September 2017

Marie-Céline Zanella; Sabine Yerly; Abdessalam Cherkaoui; Gesuele Renzi; Aline Mamin; Laura Lourenço Cordes; Elisabeth Delaporte; Zofia Baranczuk-Turska; Olivia Keiser; Jacques Schrenzel; Stephan Harbarth; Valeria Gaia; Laurent Kaiser

doi:10.4414/smw.2018.14687

Swiss Medical Weekly (Dec 2018)

A community outbreak of Legionnaires’ disease in Geneva, Switzerland, June to September 2017

Marie-Céline Zanella,
Sabine Yerly,
Abdessalam Cherkaoui,
Gesuele Renzi,
Aline Mamin,
Laura Lourenço Cordes,
Elisabeth Delaporte,
Zofia Baranczuk-Turska,
Olivia Keiser,
Jacques Schrenzel,
Stephan Harbarth,
Valeria Gaia,
Laurent Kaiser

Affiliations

Marie-Céline Zanella: Laboratory of Virology, Division of Laboratory Medicine and Division of Infectious Diseases, University of Geneva Hospitals, Switzerland; University of Geneva Medical School, Switzerland
Sabine Yerly: Laboratory of Virology, Division of Laboratory Medicine and Division of Infectious Diseases, University of Geneva Hospitals, Switzerland; University of Geneva Medical School, Switzerland
Abdessalam Cherkaoui: Laboratory of Bacteriology, Division of Laboratory Medicine and Division of Infectious Diseases, Geneva University Hospitals, Switzerland; University of Geneva Medical School, Switzerland
Gesuele Renzi: Laboratory of Bacteriology, Division of Laboratory Medicine and Division of Infectious Diseases, Geneva University Hospitals, Switzerland; University of Geneva Medical School, Switzerland
Aline Mamin: Laboratory of Virology, Division of Laboratory Medicine and Division of Infectious Diseases, University of Geneva Hospitals, Switzerland; University of Geneva Medical School, Switzerland
Laura Lourenço Cordes: University of Geneva Medical School, Switzerland
Elisabeth Delaporte: Cantonal Health Service, General Directorate for Health, Geneva, Switzerland
Zofia Baranczuk-Turska: University of Geneva, Institute of Global Health, Geneva, Switzerland; Institute of Mathematics, University of Zurich, Switzerland
Olivia Keiser: Institute of Mathematics, University of Zurich, Switzerland
Jacques Schrenzel: Laboratory of Bacteriology, Division of Laboratory Medicine and Division of Infectious Diseases, Geneva University Hospitals, Switzerland; University of Geneva Medical School, Switzerland
Stephan Harbarth: Infection Control Programme and WHO Collaborating Centre on Patient Safety, The University of Geneva Hospitals and Faculty of Medicine, Geneva, Switzerland
Valeria Gaia: Swiss National Reference Centre for Legionella
Laurent Kaiser: Laboratory of Virology, Division of Laboratory Medicine and Division of Infectious Diseases, University of Geneva Hospitals, Switzerland; University of Geneva Medical School, Switzerland

DOI: https://doi.org/10.4414/smw.2018.14687
Journal volume & issue: Vol. 148, no. 4748

Abstract

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PURPOSE Eight confirmed cases of Legionnaires’ disease were identified at the Geneva University Hospitals between 28 July 2017 and 02 August 2017, leading to a detailed outbreak investigation. METHODS Legionnaires’ disease cases were defined according to Swiss and European (ELDSNet) consensus guidelines. An outbreak investigation task force was put in place. Patients were interviewed, when feasible, with a standard questionnaire. A Legionella pneumophila urinary antigen test was performed in all cases. Lower respiratory tract (LRT) specimens were collected for culture, polymerase chain-reaction (PCR) assay, monoclonal antibody subtyping and sequenced-based typing (SBT). Multiple environmental samples were collected. Case geographical mapping was performed and local meteorological data were obtained. RESULTS Thirty-four confirmed cases of Legionnaires’ disease were identified between 20 June 2017 and 16 September 2017, including 28 patients living in the Canton of Geneva and 6 cases in neighbouring cantons and France. The case fatality rate was 8.8%. The urinary antigen test was positive in 32/34 (94.1%) cases. Among the 17/34 (50%) cases with available LRT specimens, 8 (47.1%) were culture/PCR positive, 5 (29.4%) were PCR positive only, and 4 (23.5%) were culture/PCR negative. Monoclonal antibody subtyping and SBT on 12 samples allowed subtype identification of 8 samples, with a predominance of L. pneumophila serogroup-1 subtype-France/Allentown ST23 among clinical isolates. A specific city area was identified as a possible outbreak epicentre in 25/34 (73.5%) cases, although molecular analysis of clinical and environmental specimens revealed heterogeneous subtypes of L. pneumophila. CONCLUSIONS In this largest documented outbreak of Legionnaires’ disease in Switzerland, we report prompt outbreak identification, leading to timely initiation of a detailed, well-orchestrated clinical and epidemiological investigation.

Published in Swiss Medical Weekly

ISSN: 1424-7860 (Print); 1424-3997 (Online)
Publisher: SMW supporting association (Trägerverein Swiss Medical Weekly SMW)
Country of publisher: Switzerland
LCC subjects: Medicine
Website: http://www.smw.ch

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