One very harmless Kerbal disease.

[MedwedianPresident]

Hirnrygt (Medwedian literally for "Brain Vomiting") - this is a viral disease found mainly in rural areas of northern Medwedia. Only 124 documented cases have been identified. There are several stages of it.

Stage I: Heavy bleeding out of body openings starts. Vision is blurred and movement is painful. The victim has to cough constantly, which causes the disease to be mistaken for a TB-like lung condition. The symptoms are caused because the virus orders the body to disintegrate itself.

Stage II: Vision is now restricted to blurred, black-and white pictures. Hallucinations start and the victim is very weak due to blood loss, so movement is extremely hard. Fat is lost, and many processes such as digestion are halted.

Stage III: The brain starts falling apart, and bits of it can start exiting through the mouth or ears. The victim finally dies as the control center of the body is destroyed, but the organs proceed disintegrating, with bodily fluids exiting for several days and bones transforming into a butter-like substance. Infection can occur through any contact with body fluids of the victim.

Of course, just to make it more scary, no treatment is known.