1) Infection 
In epidemiology, infectivity refers to the ability of a pathogen to establish an infection. More specifically, infectivity is a pathogen`s capacity for horizontal transmission that is, how frequently it spreads among hosts that are not in a parent-child relationship. The measure of infectivity in a population is called incidence. Infectivity has ....
1. The characteristic of a disease agent that embodies capability of entering, surviving in, and multiplying in a susceptible host. ... 2. The proportion of exposures in defined circumstances that result in infection. ... (05 Mar 2000) ... 
Type: Term Pronunciation: in′fek-tiv′i-tē Definitions: 1. The characteristic of a disease agent that embodies capability of entering, surviving in, and multiplying and causing disease in a susceptible host. 2. The proportion of exposures in defined circumstances that result in infection.
Infectivity: The proportion of persons exposed to an infectious agent who become infected by it.
The measure of the ability of a pathogen to cause infection.