An epidemic curve primarily provides information about which aspect of an outbreak?

• A. Distribution of the times of onset for cases occurring during an outbreak
• B. The geographical spread of cases
• C. The total number of deaths
• D. The average age of affected individuals

Answer: (A)

An epidemic curve is fundamentally about when cases occur. It plots the number of new cases over time, showing the distribution of onset times as the outbreak unfolds. This timing pattern helps reveal how the outbreak began and progressed, such as a sharp, short-lived spike from a point source or multiple waves from person-to-person spread.

Geographic spread isn’t shown by the curve itself; you’d need a map or space-time plot to see where cases are occurring. The total number of deaths isn’t the focus either—the curve tracks onset, not outcomes. And age distribution requires demographic breakdowns, not just the timing of onset. So the curve best conveys how cases accumulate over time, i.e., the distribution of onset times.