Few seem to remember this, but there was a short-lived experiment by SOE that involved a story line about a plague or disease running rampant through Tunaria. I believe you got the plague by simply coaching through a town that was infected, though you might have had to actually fight something with the plague. Once a few players got it, s* hit the fan.
The plague was transferable while fighting. Every time you swung your sword, a proc animation would go off showing your character casting the plague on the mob. Then, the newly infected mob, would cast it back to whoever it was hitting. Meaning that if 1 person in the group has the plague, eventually everyone in the group would have the plague. As you can imagine, this thing spread fast.
The only way to cleanse your character was to die. Besides the annoying proc animation, with its casting sounds, the plague debuffed CHA and INT. (This might not be 100% accurate.) Essentially healers and casters were up a creek.
Judging by the lack of recollection from the people I have spoken with about the plague, I’m guessing the event happened in late 2004 or early 2005. It lasted two or three months before SOE scrapped the idea. It was easily one of the biggest botched storylines in the game’s history that did more to anger players than build their interest.