Able to infect others.
Memorable and invoking excitement or interest.
Spreading quickly from one person to another.
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).
Impossible to communicate.