infectivity

Infectivity refers to how easily a pathogen, like a virus or bacterium, can enter, establish itself, and begin to multiply in a host. It’s a measure of how contagious a disease is—high infectivity means the pathogen can spread quickly because it easily infects people. Factors influencing infectivity include the pathogen’s characteristics, the way it spreads (airborne, contact, etc.), and the host’s immunity. Understanding infectivity helps public health officials assess the risk of outbreaks and develop strategies to control the spread of diseases.