swine flu history 20 million deathsThe swine flu is a descendant of the infamous "Spanish flu" that caused a devastating pandemic in humans in 1918-1919.[3] In less than a year, that pandemic killed more than 500,000 Americans and some 20 million people worldwide - the greatest number ever killed in so short a period by any natural or man-made catastrophe. It also killed and sickened large numbers of hogs. Within a decade, the disease stopped circulating among humans, but it has infected swine ever since. Although hogs had initially caught the virus from humans, it has undergone slight changes over the years, emerging occasionally to infect individuals who work closely with pigs. However, there have only been 12 cases in the U.S. since 2005 in which humans caught swine flu after being in contact with pigs and there is currently no requirement that pigs be vaccinated against swine flu. [4]
The flu virus is perhaps the trickiest known to medical science; it constantly changes form to elude the protective antibodies that the body has developed in response to previous exposures to influenza or to influenza vaccines. Every two or three years the virus undergoes minor changes. Then, at intervals of roughly a decade, after the bulk of the world's population has developed some level of resistance to these minor changes, it undergoes a major shift that enables it to tear off on yet another pandemic sweep around the world, infecting hundreds of millions of people who suddenly find their antibody defenses outflanked.[5] Even during the Spanish flu pandemic, the initial wave of the disease was relatively mild and the second wave was highly lethal.[3]
In 1957 there was an Asian flu pandemic that infected some 45 million Americans and killed 70,000 of them. Eleven years later, lasting from 1968 to 1969, the Hong Kong pandemic afflicted 50 million Americans and caused 33,000 deaths, costing approximately $3.9 billion. In 1976 about 500 soldiers became infected with swine flu over a period of a few weeks. However, by the end of the month investigators found that the virus had "mysteriously disappeared" and there were no more signs of swine flu anywhere on the post. [3] There were isolated cases around the U.S. but those cases were supposedly to individuals who caught the virus from pigs.
Medical researchers worldwide remain vigilant knowing that the swine flu virus might again mutate into something as deadly as the Spanish flu. They are carefully watching the latest 2009 outbreak of swine flu and making contingency plans for a possible global pandemic.