Which description best fits a point-source outbreak curve?

• A. Propagated: multiple waves
• B. No peak
• C. Stepwise increases
• D. Point source: sharp, single peak

Answer: (D)

This item hinges on how outbreak curves reflect how people were exposed. A point-source outbreak happens when many people are exposed to the same source over a brief period. Because exposure is concentrated and the disease has a similar incubation period, most cases occur within one incubation window, producing a sharp, tall peak that rises quickly and then falls as the source is removed or everyone at risk has fallen ill. This creates a single, narrow peak.

If it were propagated (spread person to person), you’d see multiple waves as each generation adds another rise in cases, not a single sharp peak. A pattern with no peak isn’t typical for outbreaks and wouldn’t match a defined point-source event. Stepwise increases imply intermittent exposure or ongoing transmission with distinct jumps, which also doesn’t match a tight, single-peak curve.

So the best fit is a description of a point-source outbreak curve as sharp and single-peak.