Spanish flu

The Spanish Flu Pandemic, also known as the Great Influenza Pandemic, the 1918 Flu Epidemic, and La Grippe, was an unusually severe and deadly strain of avian influenza, a viral infectious disease, that killed some 25 million to 50 million people worldwide in 1918 and 1919. It is thought to have been one of the most deadly pandemics so far in human history. It was caused by the H1N1 type of flu virus.

Mutation theory

One prevailing theory indicates that the two primary concepts in genetics created the virus at Fort Riley, Kansas--genetic drift and genetic shift. The fort bred its own swine and poultry for consumption at the fort. Like the avian flu in Asian, poultry in the United States characteristically contract a certain strain of influenza. Swine also characteristically contract a specific strain of influenza; however, the two strains (one infecting avian species, the other infecting swine) can usually cross infect the opposite species. Occasionally, usually by chance, when the viruses cross infect from one species to another, one influenza strain can incorporate the other strains properties and change drastically (so called "drift"). Under bad circumstances the new influenza can kill half-or-more of the poulty and/or swine population, but what really concerns epidemiologists is genetic "shift", which is also theorized to have occured at the fort. The strain that was jumping from swine to poultry or vice-versa jumped to humans (the genetic "shift") allowing the influenza that was confined to swine and poultry to become a human pathogen. At the same time, the new strain was highly infectious and deadly because humanity had never experienced such a strain of influenza.

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Recently, scientists (see below) have reconstructed the virus, and the evidence gained from that reconstruction suggests that the virus jumped directly from birds to humans, without traveling through the pork. This does not eliminate the idea that the pandemic started with a Fort Riley cook, however; indeed, he could've been preparing chicken when he came down with the bug.

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