and the disease itself is
I can see a disease that no one else can perceive,
Death sees life as a problem.
I have the cure and showed it so others would believe.
The cure for life is its ending, via death. Death comes to all and "cure"s them.
Through my mask I've seen it spread for centuries,
"mask" I'm not positive about, but it could be a reference to a degree of isolation, or just that Death may present a face if personified. Death has perceived life spreading for ages.
with just one touch I can solve everyone's miseries.
One touch of death and life is cured.
Though I'm locked up kept away to cure their sickness,
Those afflicted with life try to prevent death.
they are afraid of my process and call it wickedness.
Those afflicted with life fear death, and ascribe malice and evil to it.