Contagious

From Old French contagieus, from Late Latin contagiosus, from contagio.

Full definition of contagious

Of a disease, easily transmitted to others.The flu was so contagious that everybody in town got sick!
Of a fashion, laughter, etc., easily passed on to others.Wearing jeans was a contagious fad at that time.
Of a person, having a disease that can be transmitted to another person by touch.They were highly contagious, spreading bacteria to other people.