There are two main reasons why I'd rather avoid Negative Levels.
1 They are used, generally, to portray a very specific thing in the game.
2. While simpler to handle at the moment (here, take 1 Negative level), I think they are a hassle to handle in the long run, especially if affecting the player characters. Or high level NPCs like Thieves, Clerics or Magic-users.
EDIT: latest version, cleaned up the language, removed ST penalty, allows spell preparation but requires ST to avoid damage.
Cure disease cures all diseases that the subject is suffering from.
The spell also kills parasites afflicting the target creature. Certain special diseases may not be countered by this spell or may be countered only by a caster of a certain level or higher.
Note: This spell does not prevent reinfection after a new exposure to the same disease.
The reverse form of this spell, cause disease, infects the target with an ailing -and potentially deadly- disease for the next 1d6+2 days. A successful melee attack roll is required in this case, and no Saving Throw is allowed. If the attack is successful, the target is infected.
While the disease is in effect, the victim cannot benefit from natural recovery of Hit Points and Constitution points.
In addition it suffers a -2 penalty to Attack rolls and Armor Class.
At the end of each day in which an infected character exerted itself (for example by fighting, traveling, working, preparing spells or doing magical research), he or she must roll a Saving Throw versus Spells or suffer 1d6 damage points.
Once the duration of the spell is over, the affected character, if still alive, is free of the illness and can once more benefit from natural healing and undertake any activity that requires effort without fear of taking damage.
Cause disease has no effect on unliving creatures like the undead or golems.