A disease which spreads by contact:

Answer: Option C

The one word substitution is Contagious.

Incurable : (of a sick person or a disease) not able to be cured.
Infectious : (of a disease or disease-causing organism) liable to be transmitted to people, organisms, etc. through the environment.
Fatal : leading to failure or disaster.
Contagious : (of a disease) spread from one person or organism to another, typically by direct contact.