1. The state or condition of being contagious, easily transmitted to others
   "Without factoring in the contagiousness of a disease, we will probably underestimate the effect that curing someone with a given disease may have"
    
2. The quality of being easily transmitted from one person to another
   "The contagiousness of the virus led to rapid spread in the community"

Type of: harmfulness, noisomeness, noxiousness

Encyclopedia: Contagiousness