In medical epidemiology, prevalence is defined as the proportion of the population with a condition at a specific point in time (point prevalence) or during a period of time (period prevalence). [1] Prevalence increases when new disease cases are identified (incidence), and prevalence decreases when a patient is either cured or dies.  Many times, the period prevalence will provide a more accurate picture of the overall prevalence since period prevalence includes all individuals with the condition between two dates: old and new (incident) cases, as well as those who were cured or died during the period. [2][3]   Clinically, prevalence is most commonly described as the percentage with the disease in the population at risk.   We commonly hear this in everyday discussion, and most find these references intuitive to interpret, such as "currently, X% of Americans were overweight or obese."