Virtual plague
Another one of those cool emergent behaviors that sometimes happen in massively multiplayer games. This time, there's a blood infection that is spreading throughout the land in World of Warcraft.
If an infectous disease is this hard to control in a virtual world where the programmers are, literally, God, what chance do we really have if an avian flu pandemic takes hold in the non-virtual world?
Source: Virtual plague spreading like wildfire in World of Warcraft