Image contains four separate types of epi curves.1 - Point source, where there is a single peak in cases over a short period of time. 2 - Continuous source, where there are relatively stable counts of cases over a long period of time. 3 - Propagated source, where there are multiple peaks of cases that may be separated in time, and often increasing in magnitude. 4 - Intermittent source, where multiple point-source curves appear over time, with gaps between them.