What is the meaning of Infectious?

Caused by an agent that enters the host's body (such as a bacterium, virus, parasite, or prion); often, also, transmitted among hosts via any of various routes (for example, contact, droplet-borne, airborne, waterborne, foodborne, fomite-borne, or bloodborne).

Able to infect others; capable of transmitting pathogens.

Spreading quickly from one person to another.