contagious(of a disease, easily transmitted to others) adjective [UK: kən.ˈteɪ.dʒəs] [US: kən.ˈteɪ.dʒəs]Enthusiasm is contagious. = El entusiasmo es contagioso.
infectious(able to infect others) adjective [UK: ɪn.ˈfek.ʃəs] [US: ˌɪn.ˈfek.ʃəs]Laughter is infectious. = La risa es contagiosa.