Spatial pattern of all cause excess mortality in Swiss districts during the pandemic years 1890, 1918 and 2020

Background: Every pandemic is embedded in specific spatial and temporal context. However, spatial patterns have almost always only been considered in the context of one individual pandemic. Until now, there has been limited consideration of spatial similarities or differences between pandemics. Objective: The aim of this study was to examine spatial pattern of excess mortality in Swiss districts during the pandemic years 1890, 1918 and 2020. In addition, determinants that could explain the difference between districts were analyzed. Methods: Excess mortality rate was estimated using a Bayesian spatial model for disease mapping. A robust linear regression was used to assess the association between ecological determinants and excess mortality. Results: The highest excess mortality rate in all districts occurred during the 1918 pandemic, the lowest excess mortality rate was seen for the 1890 pandemic. Moreover, this analysis revealed heterogeneous spatial patterns of excess mortality in each pandemic year. Different socio-demographic determinants, in each pandemic, might have favored excess mortality. While the age composition, cultural and area-based socio-economic position differences and the proximity to France and Italy were the main determinants of excess mortality during the Covid-19 pandemic, the mobility, preexisting health issues (i.e. TB) or the remoteness location in the mountains played crucial roles during the historical pandemics. Contribution: The analysis of spatial patterns in pandemics is important for public health interventions in future pandemics or outbreaks since it helps to identifying patterns of transmission. Identifying and understanding geographic hotspots informs precise interventions, aids in public health implementation, and contributes to tailored health policies for the region. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This study was funded by Foundation for Research in Science and the Humanities at the University of Zurich (Grantee Kaspar Staub, Grant-No. STWF-21-011); University of Geneva & University of Zurich Strategic Partnership Cofunds (call-2020#5, Grantees Kaspar Staub, Olivia Keiser, Frank Rühli, Antoine Flahault). ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced are available online at https://github.com/KaMatthes/UZH\_UniGe\_Past_Pandemics