I took him to a restricted area, reprimanded him, and "cleansed" [ read: killed ] him of the bug so that he would no longer infect anyone. The rest of it was sent to the developers to look at. The affected people and dungeons are quarantined off from affecting more NPCs and PCs. It should be fixed next patch if the developers are good enough.

[ He stands firm on "pay me double" about actually getting rid of bugs on a wider scale. ]