The Likelihood of a Host-To-Host Epidemic is Highest When

Question

The likelihood of a host-to-host epidemic is highest when:
A) the proportion of immune individuals in a population is below the epidemic threshold.
B) the proportion of immune individuals in a population is above the epidemic threshold.
C) the proportion of immune individuals in a population is at the epidemic threshold.
D) anytime the proportion of immune individuals in a population rises above 50%.
E) the second time a pathogen is introduced into a particular population.

Accepted Answer

The epidemic threshold is the proportion of immune individuals in a population above which an outbreak is unlikely to occur. Therefore, when the proportion of immune individuals in a population is below the epidemic threshold, there are not enough immune individuals to prevent the spread of the pathogen and an epidemic is more likely to occur.