What is an epidemic curve?

• A. Disease frequency data when a disease is first recognized in a population plotted across time
• B. A map of geographic distribution
• C. A chart of vaccination coverage over time
• D. A table of symptoms by patient

Answer: (A)

An epidemic curve is a graph of disease frequency over time, typically showing the number of new cases by day or week as an outbreak unfolds. It starts from when the disease is first recognized in the population and helps reveal the outbreak’s pattern—sharp peaks suggest a point-source exposure, multiple waves imply person-to-person transmission, and a long plateau can indicate a continuous source or sustained transmission. The data come from onset dates of illness (not geographic location or vaccination status, and not a table of symptoms). This makes it the correct description: a time-based plot of new cases.