While working at the Rockefeller Institute at Princeton, with his mentor Dr Paul Lewis, (who earlier had discovered the polio virus), virologist, Dr Richard Shope successfully isolated the “virus of swine influenza”, the first virus ever isolated. He submitted his work [2, 3] on May 6, 1931, for publication. [1] Influenzae virus is from family Orthomyxoviridae.
“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”
Initially Shope and Lewis isolated a bacterium resembling Pfeiffer’s bacillus [4] (the bacterium was then classified Bacterium influenzae suis, and now Haemophilus influenzae), but when they injected the bacteria into pigs, it did not cause disease. Then Shope used a filtrate, which caused a highly contagious, influenza-like disease in pigs—albeit a more mild one than seen in naturally-infected pigs,” but “mixing the filtrate with the bacterium reproduced the severe disease.” [1]
In 1933 an influenza virus was isolated from a human influenza patient and in infected ferrets it produce influenza symptoms, which was was repeated several more times.
They hypothesise that the 1918 pandemic virus is an ancestor of this swine virus. It was said in 1918 that the “clinical manifestations resemble those observed in the pandemic 1889-1894″, which could mean the causal agent is endemic, and that severe disease may have more to do with an associated bacterium at the time of infection. After all the 1918 pandemic deaths were mostly caused by bacterial pneumonia, and mass bacterial vaccinations (typhoid, pneumonia, “influenza”) were administered prior and during disease outbreak.
As of 1960 “it is well recognized that pneumonia is the main cause of death from influenza, and observations during the pandemic of 1918-1919 indicated that secondary or concomitant bacterial infection of the lung was almost always present in fatal cases.” [6]
In 1892 Dmitri Ivanovski discovered an “extremely miniscule infectious agent”, smaller than bacteria, while working on tobacco disease. In 1898 Martinus Beijerinick replicated Ivanovski’s work, and coined the term “virus”. Historically, the term virus had the latin meaning of “poisonous substance”, an important point to note when reading historical medical publications. [5]