In case you ever wanted to see some nice theory + simulation + visuals here’s a collection of nice Mathematica based explorations:

Jeff Bryant with Ed Pegg’s code on Influenza Epidemic modeling
SARs spread demonstration/animation
Oh, and I thought this was interesting… a nice PPT on pandemics.
I wonder if the swine flu spread through social networks with a similar dynamic? hmmm… Perhaps one should dig through this code for mining Twitter with Mathematica and start connecting the dots. How could we do this? We need to pull down a lot of tweets. and we need some way to codify them by location or friends/groups. What would we consider “spreading”. Is it posting a link? replying to someone? hmmm. Maybe this is a big fat waste of time….