Contagious
WordNet
adjective
(1) (of disease) capable of being transmitted by infection
(2) Easily diffused or spread as from one person to another
"A contagious grin"
WiktionaryText
Adjective
- Of a disease, easily transmitted to others.
- Of a fashion, laughter, etc., easily passed on to others.
- Of a person, having a disease that can be transmitted to another person by touch.