Influenza is a zoonotic viral disease that represents a health and economic threat to both
humans and animals worldwide. Swine influenza (SI) was first recognized clinically in pigs
in the Midwestern US, in 1918, coinciding with the human influenza pandemic known as the
Spanish flu. Since that time SI has remained of importance to the swine industry throughout
the world. In this review, the epidemiology of swine influenza virus (SIV) infection in North
American pigs is described in detail. The first 80 years of SI remained relatively static …