1) A non-life threatening ailment, similar to a cold, that infects your body. It does not hurt you enough to make you miserable, but just enough to piss you off. Little trollfaces swim through your veins and inject RAEG into your cells. They then explode to create more troll faces in bursts of "LOL U MAD?". It is easy to get rid of, but impossible to ignore.
2) When a swarm of trolls target a specific forum board or chat room and bombard it with messages.
3) A virtual ailment that affects the user by making them have the constant urge to troll people. Whether it be trolling stupid people or even other trolls, everyone could be your target. This disease is impossible to get rid of, but there are many so-called "remedies". It is believed to have first spread in 4chan, but its real origins are unknown.
I got the Troll Virus, dude. I needed to yell at someone.