In 1931, Rockefeller Institute investigator Richard Shope published the first of three landmark papers that established the etiology of ‘swine influenza,’ the epizootic disease of pigs that had first been noted during the fall wave of the 1918 influenza pandemic.

Pig farmers in Iowa had reported two outbreaks—one in 1918 and another in 1929—of a highly contagious, influenza-like disease among their animals. The disease bore such a remarkable resemblance to human flu that it was named swine influenza.

Both Shope and the British trio of Wilson Smith, Christopher Andrewes, and Patrick Laidlaw later demonstrated that sera from humans that were infected with the 1918 flu virus could neutralize the pig virus, leading them to conclude that the swine virus was a surviving form of the 1918 human pandemic virus (H1N1). In fact, a related strain of flu still circulates among pigs today and the danger of a future pandemic grow with increased international air travel and human contact with waterfowl and avian influenza (H5N1).