Gentlemen, I suggest you research the Spanish flu epidemic around WW1. That thing was nasty. I think the only parts of the world not exposed to it were some Pacific Islands in Indonesia and Micronesia. There was a huge deal about it a few years ago when SARS was in the news. Researchers found, and dug up, a few Alaskan indigenous people's graves who had it. Found how the lung tissue was affect and why it was so deadly at the time.
End result, that epidemic was an incredibly weak H1N1 bug compared to the modern strains of influenza.
My little theory on the next world pandemic. It'll happen around Xmas or another major holiday when there's ton of air travel. It'll have a fairly long early infection period whereby the person who's infected will only have a few headaches, feel achy, but be good enough to go to work and infect everyone around them.
College kids returning to school after Xmas break will be able to inoculate millions with the new virus. There's about 17 million college students in the US.
The incubation period/early infection will allow air travelers to spread it from continent to continent. The fact they're traveling during Xmas will push them to visit their relatives anyway, and get a little Thera-Flu to get them through the trip.
The bug doesn't even need to be that tough to exist outside of the host for any amount of appreciable time. It does need to be able to jump back and forth between species though. Birds of course are the worst case scenario, but your pet cat/dog would be a second worst case. If it hits domesticated felines, and then jumps to a tertiary vector, you'll never quarantine it.
Nevermind. Ignore everything I wrote. I'm keeping it as a secondary plot line for a future novel. All copyrights and privileged reserved by author.
I hate using wiki, but here's a note on the H1N1 of the day.
http://en.wikipedia.org/wiki/1918_flu_pandemic