Speaking of epidemics and pandemics , there are of course simulations of epidemics and how they spread. The largest individual-based epidemiology simulation computer model right now seems to be "Episims", and the findings drawn from running Episims are quite interesting. One of these findings is an illustration of how diseases spread exponentially, such that isolating individuals is not as effective as how quickly authorities act.

Take a look: If Smallpox Strikes Portland...