Article Text

Download PDFPDF
Legionella bacteria in shower aerosols increase the risk of Pontiac fever among older people in retirement homes
  1. M Bauer1,2,
  2. L Mathieu3,
  3. M Deloge-Abarkan1,2,
  4. T Remen1,2,
  5. P Tossa1,2,
  6. P Hartemann1,2,
  7. D Zmirou-Navier1,2
  1. 1
    Nancy-University School of Medicine, Département Environnement-Santé, Vandoeuvre-lès-Nancy, France
  2. 2
    INSERM, Vandoeuvre-lès-Nancy, France
  3. 3
    Ecole Pratique des Hautes Etudes (EPHE), Laboratoire d’Hydro-climatologie Médicale Santé Environnement, Vandoeuvre-lès-Nancy, France
  1. Dr L Mathieu, Laboratoire d’Hydro-climatologie Médicale Santé Environnement, School of Medicine, 9 avenue de la Forêt de Haye, 54500 Vandoeuvre les Nancy, France; laurence.mathieu{at}


Background: 828 elderly subjects residing in nursing homes were followed up during 4 months to ascertain incidence of symptoms associated with Pontiac fever (PF) in a non-epidemic setting.

Methods: The exposure situation was inhalation of Legionella bacteria while showering. An audit of the hot water system in all institutions allowed ascribing each subject to a water quality area wherefrom one shower was sampled for Legionella assays at the end of the follow-up period. Legionella were detected in water and aerosols using the culture (CFU, colony forming units) and in situ hybridization (FISH) techniques.

Results: Among 32 Pontiac-like episodes, 29 cases complied with the operational definition of PF elaborated for this study. Incidence density was 0.11 case/person–year (95% CI 0.07 to 0.15). Water concentrations greater than 105 Legionella FISH/l and 104 Legionella CFU/l were associated with an increased risk of PF (respectively RR 2.23, p = 0.05 and RR 2.39, p = 0.11, with significant dose–response patterns: p for trend <0.04). The condition also seems associated with aerosol concentrations above 103 Legionella FISH/l of air. A significantly higher risk of Pontiac-like episodes (RR 6.24, 95% CI 2.12 to 18.38) was seen for elderly subjects receiving corticosteroid therapy.

Conclusion: The water and threshold values identified in this research could be used to inform guidance measures aimed at protecting institutionalised older people from Legionnaires’ disease. Immunosuppressive therapy in the same population group can significantly enhance susceptibility to Legionella bacteria.

Statistics from

Request Permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.


  • Funding: This study was funded by AFSSET (French Agency for Environmental and Occupational Health Security) (Grant number: RD-2002-015 and RD-2003-009), the French Ministry of Health and Veolia Environnement. Magali Deloge-Abarkan was recipient of a doctoral scholarship from ADEME and EDF. These funding sources were not involved in the study design, in the collection, analysis and interpretation of the data, or in the decision to submit the paper for publication.

  • Competing interests: None.

  • Ethics approval: Ethics approval was obtained.

Linked Articles

  • In this issue
    Mauricio L Barreto