Cure

A Cure type spell is one that fixes a certain ailment. The most common cure spells remove poison and/or disease counters from a target, as described below. But other cure type spells exist to cure certain issues, such as blindness.

Almost all lingering spells based off of Poison or Disease have counters associated with them. As soon as you can remove all the counters, the spells effect ends, regardless of how much time it should otherwise last.