Seasonal Mortality Patterns

The Southern Hemisphere provides a natural test of seasonal causation because its winter occurs at a different time of year than the Northern Hemisphere. Pre-pandemic death rate data from 2015 to 2019 establishes the winter-peaking baseline used to evaluate post-pandemic excess mortality. Baseline mortality, including from heart disease, peaks consistently every winter as a normal recurring feature. Excess deaths in Northern Hemisphere countries increase as the year approaches winter, consistent with baseline seasonal mortality increases.