As Contagion, but with an added effect. If healed through the magical, spell-like or supernatural actions of another person, the unlucky person who cures the affliction must make a fortitude save (vs. this spell) or contract the same illness himself! Note that if the target heals himself through magic of any sort, he can catch the secondary infection himself.
The original target may make a fortitude save avoid the initial disease. If successful, the target must also make a will save, or else the next person who magically cures him of anything in the next 1d3 weeks may contract the disease, as above.
The disease is not transferred if a curing attempt fails. Also, a wish, limited wish or miracle can be worded to prevent the disease transfer. Your DM may devise other safe curing methods, or disallow the ones presented here.
Spell resistance applies to every situation where a saving throw is called for.
The target radiates faint necromantic magic while "contagious".