Infectious

Adjective

1. 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).

   "Cancer is usually not infectious."

2. Able to infect others; capable of transmitting pathogens.

   "Despite feeling better, the patient is still infectious."

3. Spreading quickly from one person to another.

   "infectious smile"

4. Memorable and invoking excitement or interest.

   "Pop music is more infectious than elevator music."