<span>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. </span>
Excitatory neurotransmitter? This question is too vague.
