Which sentence correctly describes the difference between incidence and prevalence?

• A. Incidence measures all cases that ever existed in history, and prevalence measures only cases that will occur in the future.
• B. Incidence measures new cases over a specified time among those at risk, while prevalence measures all existing cases (new and preexisting) at a particular point or period in the population.
• C. Incidence and prevalence are synonyms and can be used interchangeably to mean any count of disease regardless of time or population at risk.
• D. Prevalence describes only severe cases while incidence reports only asymptomatic infections; the two are unrelated temporal measures.

Answer: (B)