Joybug infection is called "the happy death" on Mongo, because it secretes a venom that makes the victim experience complete euphoria before dying. To keep a victim alive, his caretakers have to keep him from experiencing any happiness.
The children of Mongo have a nursery rhyme: "When bit by the bug, all joy will destroy. But cause pain and sorrow, they may see tomorrow. When bit by the bug, only strife will save life."
The only people who know how to cure the joybug infection are the Omadrians.