This year marks the 70th anniversary of the first documented isolation of equine influenza virus (EIV). In May 1956, major outbreaks of respiratory disease in horses took place in the former Republic of Czechoslovakia. The presence of antibodies against influenza A in serum from affected horses, together with observed similarities in clinical course with influenza in humans, led Sovinova and colleagues to “investigate the problem in greater detail”. Most nasal washes cultured in embryonated chicken eggs failed due to contamination, but sample 262 remained sterile, yielding A/equine/Prague/56 (H7N7), marking the start of EIV research and initiating a new area of influenza research. While poultry and swine are also kept in dispersed, interconnected populations, horses uniquely combine those characteristics with a long lifespan and global mobility (trailing only humans as the most common commercial air travellers, for breeding and performance purposes), an intersection of epidemiological features that more closely resembles that of humans and makes EIV a particularly informative model system. This Pearl article is our personal view that aims to highlight how studies on EIV have informed fundamental concepts of influenza virus biology, evolution, and epidemiology.