What's the worst disease to have?

I don't know what you mean by worse.  I think that any disease in which the doctors say... "I'm sorry, but there's nothing we can do... you only have this much time to live"  is the worse.  Don't you think?

I would think that some forms of cancer would be the worst.  They can last for years, with increasing amounts of pain (although it can somewhat be ameliorated with narcotic pain relievers).

The worst that I've seen is lung cancer; it is agonizing, and can last for years and years. 

Mouth cancer which has been treated with removal of the jaw and part of the face, is probably the most disfiguring, and thus psychologically devastating.

 A related cancer is that of the sinuses (chondrosarcoma). Most doctors won't even try to treat thse poor victims, as it can involve removal of the entire face--including the eyes, jaws, lower forehead.  The one case I've heard of, the patient wanted to do everything possible.  They were able to manufacture a prosthesis to cover the cavity thus caused, but I cannot imagine a more devastating way to live.

Pancreatic cancer is extremely painful, but these patients usually only live for about 6 months, so they don't have such a long time to suffer.

See any disease unattended can become worst . If you take precautions at intial stages then every disease can become curable . Even though if you consider Aids, Cancer ,etc are the worst diseases.