The problem is that pigs are highly susceptible to the flu, and our filthy farms probably have just as much potential to have been the source as Mexico was.
I don't doubt your numbers, but I wouldn't be shocked if panic is inflating them somewhat. That said, this does have the potential to get very scary very fast, so heed all the warnings.
I live in an Asian neighborhood, and they've already got the surgical masks whipped out. I've been working a lot lately and hadn't been paying attention to the news, so I thought SARS was making a comeback when I first noticed all the masked faces.