infectious

Etymology

adj

1. (pathology, of an illness) 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.
   More infectious diseases like the flu are usually less potent.
2. (pathology, of a person) Able to infect others.
   Despite feeling better, the patient is still infectious.
3. (of feelings and behaviour) Spreading quickly from one person to another.
   Her enthusiasm for work can be really infectious.
4. (informal) Memorable and invoking excitement or interest.
   Pop music is more infectious than elevator music.