C. virulence
Virulence is a measure of the severity of disease that a pathogen can cause in a host. It refers to the degree of pathogenicity and the ability of the organism to cause disease symptoms. While infectivity refers to how easily a pathogen can spread, and pathogenicity indicates whether a pathogen can cause disease, virulence specifically assesses the intensity and severity of the disease caused. Latency is a different concept that refers to a state where the pathogen is present in the body but does not cause active disease.