This little piggy went to market, this little piggy stayed home and this little piggy … gave us swine flu? Wrong.

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It's a corporate marketing department's worst fear: A negative event that has little or no connection to a product becomes inextricably tied to it. So imagine how the pork industry felt when a new virus was discovered in the spring of 2009 in a small Mexican village and shortly thereafter became known as "swine flu."

The thing is, swine flu already existed, and pig farmers regularly immunize their pigs against it. Much like flu viruses pass between humans, swine flu passes between pigs. This new type of virus has shown no signs of passing from pigs to humans, but once it was christened "swine flu," that moniker stuck.

Coupled with a lack of information about this new form of swine flu was its well-documented spread among humans. As the world saw more and more newspaper headlines about this contagious illness, the price of pork dropped, as did the price of various feeds used by pig farmers, due to the sharp drop in demand for their product. Some countries banned the importing of pork from nations where swine flu appeared. Egyptian authorities took it one big step further, ordering the slaughter of hundreds of thousands of pigs. All this, without any pigs actually having this form of swine flu.

It's not at all unheard of for viruses to pass from animals to humans. In particular, you may remember warning about avian flu from a few years ago. Unlike swine flu, avian flu is known to pass from birds to humans.

But what do birds have to do with swine flu? And if pigs aren't giving it to us, where did the name come from in the first place? Keep reading to find out.