Epidemiology: Incidence and Prevalence · USMLE Step 1

A researcher finds that the period prevalence of flu during winter is higher than the point prevalence measured on a single day in winter. Why?

  1. Because flu incidence temporarily drops to zero
  2. Because period prevalence counts all cases during the season
  3. Because point prevalence includes far more individuals
  4. Because point prevalence measures only new cases
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Correct answer: Because period prevalence counts all cases during the season

Period prevalence counts all cases present at any time during the period, making it higher than point prevalence measured at a single moment.

Difficulty: Medium Question 13 of 20

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