Earlier timing of seasonal respiratory infections and seasonal mortality during the COVID-19 pandemic

Seasonal respiratory infections typically surge within a limited time window, but the exact timing within a given year is hard to predict. The disruptions caused by the COVID-19 pandemic led to dramatic changes in the transmission dynamics of many pathogens, providing a unique opportunity to study the determinants and robustness of the seasonal timing of epidemics. Combining detailed data on acute respiratory infections from Germany with an epidemiological model, we analyzed changes in the timing of seasonal epidemics. The seasonal surge in infections occurred substantially earlier during the COVID-19 pandemic, and was reflected in a corresponding shift in the seasonality of all-cause mortality. We show that this is a consistent, but transient outcome of disrupted epidemic seasonality, predictable from basic epidemiological principles.