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Swiss Med Wkly. 2018 Dec 2;148:w14687. doi: smw.2018.14687. eCollection 2018 Nov 19.

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

Author information

1
Laboratory of Virology, Division of Laboratory Medicine and Division of Infectious Diseases, University of Geneva Hospitals, Switzerland; University of Geneva Medical School, Switzerland.
2
Laboratory of Bacteriology, Division of Laboratory Medicine and Division of Infectious Diseases, Geneva University Hospitals, Switzerland; University of Geneva Medical School, Switzerland.
3
University of Geneva Medical School, Switzerland.
4
Cantonal Health Service, General Directorate for Health, Geneva, Switzerland.
5
University of Geneva, Institute of Global Health, Geneva, Switzerland / Institute of Mathematics, University of Zurich, Switzerland.
6
Institute of Mathematics, University of Zurich, Switzerland.
7
Infection Control Programme and WHO Collaborating Centre on Patient Safety, The University of Geneva Hospitals and Faculty of Medicine, Geneva, Switzerland.
8
Swiss National Reference Centre for Legionella.

Abstract

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.

PMID:
30552854
DOI:
10.4414/smw.2018.14687

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