Please choose the answer that best completes the blanks of this sentence in the correct order. The percentage of the population with a particular disease at any point in time is the ___ of disease, whereas the number of new cases over a given time period is the _ of disease.
a. prevalence; incidence
b. incidence; propagation
c. incidence; prevalence
d. mortality rate; incidence

In epidemiology, the prevalence can be defined as the proportion of a population affected by a particular medical condition such as disease or any kind of risk factor like smoking. It can be estimated by comparing the number of people found to be affected by the condition with the total number of people taken as the sample for the study. It can be expressed in percentage or fraction. Point prevalence can be defined as the condition of the population at a specific point in time.

Incidence in epidemiology can be defined as the measure of the probability of occurrence of particular medical conditions in a population within a concerned period. In other words, it can be described as the number of new cases of medical condition during a concerned period. It is expressed in proportion.