Undead affected by disease?

[PvK]

Seems to me diseases do damage to non-undead, and that damage (1 point per month) is what can cause additional afflictions. Undead with diseases don't take that damage, so they also don't gain any more afflictions from them.

However, a living leader with a disease and a Ring of Regeneration, will lose 1 point per turn but gain it back each turn, but that 1 point it loses may cause a new affliction, which isn't healed by Regeneration.

PvK