I was around for this. It was amazing fun. It really made the world (of warcraft) feel more.. alive somehow. You'd do everything you could to avoid infected players, I'd only play on an alt since my main was parked in Stormwind when the epidemic broke. I just stayed hidden away in the more obscure levelling zones and survived. It's a shame stuff like this doesn't occur more often, it really adds flavour to the game.