Description
Introduction: Notification rates for Legionnaires’ disease (LD) in Switzerland are continuously rising. In 2022, Switzerland recorded 6.7 cases/100,000 population, one of the highest annual LD notification rates in Europe. Environmental changes may further affect the incidence of LD, e.g. through increasing bacterial abundance, higher bacterial concentrations in the environment or by facilitating transmission. To better understand the epidemiology of the disease in Switzerland our research group investigates the trajectory from exposure to Legionella spp. to final and mandatory reporting of LD cases to the Swiss notification system for infectious diseases and analyse the spatial distribution of notified LD cases across Switzerland. Herein, we present findings on LD disease occurrence at cantonal and regional levels and describe the impacts of weather and climate as large-scale areal determinants of disease on the regional and seasonal distribution of LD cases.
Methodology: First we investigated trends and spatial distribution in disease notification from 2017 to 2021. A hotspot analysis mapped LD cases and identified regional clusters. We applied an ecological model to identify environmental determinants on case frequency at the district level. We then ultimately applied a case-crossover design to analyse the data using distributed lag non-linear models to identify short-term associations between seven meteorological variables and LD occurrence.
Results: We observed a north-south gradient in notification rates in Switzerland. The Canton of Ticino in southern Switzerland was identified as a hotspot in the cluster analysis (standardised notification rate: 14.3 cases/100,000 inhabitants). The strongest association with LD frequency in the ecological model was found for large-scale factors such as weather and air pollution. The case-crossover study confirmed the strong association of elevated daily mean temperature (odds ratio (OR) 2.8; CI: 1.7, 4.7) and mean daily humidity (OR: 1.5, CI: 1.2, 2.0) 6-14 days before LD occurrence, and suspected effects of air pollution on notification rates. A small literature review revealed a very limited debate on the potential impact of global warming on LD frequency and scarce literature on the occurrence of Legionella and legionellosis in warm/hot climates.
Conclusion: Weather with a specific temporal pattern of warmth and humidity before the onset of LD appears to be a determinant for disease in Switzerland; the finding provides insights into a possible effect mechanism. The relationship between air pollution and LD and the interplay with short-term weather phenomena – in the context of global warming – should be further investigated.
Publications:
Temporal trends in legionellosis national notification data. F.B.Fischer, D.Mäusezahl, MN.Wymann, Int. J. Hygiene and Environmental Health, 2022
Legionnaires’ disease in Switzerland: A prospective national case-control and molecular source attribution study (SwissLEGIO) F.B.Fischer, M.Bigler, D.Mäusezahl, et al, Infection, 2023
| Contact Geneva Health Forum | I just want to receive information about the GHF 2024 conference / Je souhaite simplement recevoir des informations sur la conférence GHF 2024 |
|---|
