With every winter comes flu season. What does that mean? Between larger pandemic outbreaks like the 1917 Spanish flu and a few others since, we run into seasonal epidemics of the disease. Influenza is far from a steady presence in our lives throughout the year; in Canada, seasonal influenza is a phenomenon that ramps up every November, peaks in the winter, and all but disappears come summertime. What causes this cycle, and, following the disruption of the COVID-19 pandemic, how will it be altered in future years?