When a disease can be passed from person to person, it is referred to as a disease.
communicable disease
non-communicable disease
fast moving disease
communicated disease

A communicable disease is a disease that can be passed from person to person. It can also occur from an animal to a person or vice versa. Airborne viruses, bacteria, blood, and bodily fluids can cause the spread of these diseases. When things are infectious or contagious it also refers to communicable diseases. The most common communicable disease is the flu, which can easily spread in an enclosed environment with a recycled circulating air (e.g. air-conditioning). Infectious disease caused by blood contact like HIV/AIDs are also dominant in society.   

Ithink that it is the brain.