A communicable disease is an illness due to a specific infectious agent or its toxic products that arises through transmission of that agent or its products from an infected person, animal, or reservoir to a susceptible host, either directly or indirectly through an intermediate plant or animal host, vector, or the inanimate environment.

Communicable diseases are infectious.   An infectious disease is a disease communicated from one person to another usually via a bacteria, protozoan, fungi, or virus that enters the human body.