This isn't genetically engineered, it's a side effect of bad farming practices.
In the same way we've managed to infect our pigs with MRSA http://www.nytimes.com/2009/03/15/opinion/15kristof.html I think we've managed to kick up yet another variant..
Signs are pointing to a Smithfields Farms hog-farm in Veracruz where the outbreak originated. http://www.grist.org/article/2009-04-25-swine-flu-smithfield/
I'm not arguing for us to go back to sticks and weeds for our food supply, but if you set up a farming environment where the only way to guarantee survival of your animals is continual, therapeutic antibiotics, you're doing it wrong.
There are two ways to write error-free programs; only the third one works.