X and Y Axes

An epidemic curve, or “epi curve,” is a visual display of the onset of illness among cases associated with an outbreak. The epi curve is represented by a graph with two axes that intersect at right angles.

The horizontal x-axis is the date or time of illness onset among cases.

The vertical y-axis is the number of cases.

Each axis is divided into equally spaced intervals, although the intervals for the two axes may differ.