While suffering from Miasma, you have -5 Health degeneration. Miasma spreads between creatures of the same kind.
Concise: You have -5 Health degeneration. Miasma spreads between creatures of the same kind.
While behaving very similar to Disease, Miasma is not a condition. It also is neither an enchantment nor hex, so there is no way for players to remove this effect by themselves. Fortunately, it will wear off after some time, and it can be removed with the Blessing of the Kirin. It appears as purple clouds close to the ground.
Creatures affected by miasma are surrounded by a green smoky cloud and a swarm of flies, the same artwork as Disease.