While g a deadly disease is certainly an admirable goal, it's also very broad and non-specific.
There are lots of fields that make contributions to medicine. If you're interested in dealing with patients directly, then pursuing the MD (or MBBS) is probably the best option. There are a lot of branches to from there that deal with specific diseases, but most often the front line medical doctors aren't so much the ones developing the cures as they are the professional that administer existing cures once they've been developed by other scientists.
As far as the scientists go who work on the cures and management strategies, you've got a veryt broad choice as well. For example if you're interested in drug development you might want to look at pharmacology, biochemistry, or chemical engineering. If you're interested in applications of nanotechnology in medicine, you could look into materials science, chemistry, chemical engineering, physics. I think really you have start by figuring out what kinds of problems you enjoy working on and then growing from there. And remember that we've more-or-less moved past the days of a lone scientist working in a lab trying to discover a cure. Now there are teams of scientists that work together to translate knowledge developed at the fundamental level into experimental models, then clinical trials and eventually translating all of that into the clinic.