Final answer:
Plotting an epidemic curve helps determine the outbreak type and the median incubation period of the disease, making options a and c correct, with the answer being (d). The curve does not show herd immunity, hence options b and e are not correct.
Step-by-step explanation:
In the study of an outbreak of an infectious disease, plotting an epidemic curve is useful for multiple reasons. Option (a) is correct; it helps determine the outbreak type, such as whether it was caused by a single source or through person-to-person transmission. Option (c) is also correct; the epidemic curve can assist in determining the median incubation period of the disease. Therefore, the correct answer is (d), which combines both options a and c. However, the epidemic curve alone does not show whether herd immunity has occurred, which rules out options (b) and (e).
Epidemiologists use the data reflected in an epidemic curve to develop strategies for interventions, such as vaccinations, to reduce disease incidence or prevent its spread. Identifying the type of outbreak and the median incubation period are key factors in designing these public health policies and immediate measures to control an outbreak.