The health and demographic impacts of the "Russian flu" pandemic in Switzerland in 1889/1890 and in the years thereafter.

Our study aims to enhance future pandemic preparedness by leveraging insights from historical pandemics, focusing on the multidimensional analysis of past outbreaks. In this study, we digitised and analysed for the first time aggregated mortality and morbidity data series from the Russian flu in Switzerland in 1889/1890 and subsequent years to assess its comprehensive impact. The strongest effects were observed in January 1890, showing significant monthly excess mortality from all causes compared to the preceding five years (58.9%, 95% CI 36.6 to 81.0). Even though the whole of Switzerland was affected, the impact varied regionally due to ecological variations. Deaths from other conditions such as tuberculosis and heart disease also increased during this period. A significant drop in birth occurred 9 months later, in the autumn of 1890. Morbidity estimates by physicians suggest that around 60% of the Swiss population fell ill, with regional discrepancies and earlier outbreaks among postal workers (1-2 weeks earlier than the rest of the population). A subsequent spike in all-cause excess and influenza mortality was recorded in January 1894 but more localized than in 1890. Our findings show no cross-protection between the 1890 and 1894 outbreaks.