U-M medical historian Howard Markel, M.D., Ph.D., discusses how at the beginning of the COVID-19 pandemic cities and states hit hard by the virus ‘flattened the curve’ of a rising tide of cases by cutting back on the kinds of interactions that can spread the virus, the same steps that worked against the flu pandemic in 1918-1919. Markel helped coin the phrase ‘flatten the curve’ based on the 1918 pandemic, and discusses the ‘three D’ model, which reduces duration of people being together, distance between people, and number of people that people interact with.