People were very concerned about another outbreak of swine flu. All care providers were asked to report, without individual names, any new cases to the public health department for tracking. Which would be most helpful for the local media to report to keep citizens informed?

Correct Answer: A

Rationale: As only new cases were being reported to the health department, the media could only report the ongoing incidence rate, that is, the number of new cases reported each day. The prevalence rate is the number of all cases of a specific disease or condition in a population at a given point in time which would not assist in knowing the number of new cases. Those infected with the flu may or may not be hospitalized or have died from the flu.

Correct Answer: B

Rationale: In epidemiology, the 'population at risk' is the group susceptible to the outcome of interest (e.g., those who could develop lung cancer in a smoking study). Choice B correctly defines this as those who may experience the outcome. A focuses on behavior, not susceptibility. C implies harm from the study itself, not the outcome. D refers to relative risk, a measure, not the group definition.

Correct Answer: A

Rationale: Endemic (A) describes a disease consistently present at a stable level in a population (e.g., malaria in some regions). B is an epidemic, C an emerging disease, and D eradication.

Correct Answer: B

Rationale: Case fatality rate (B) measures severity as deaths among cases (e.g., Ebola). A is new cases, C is total cases, D is deaths broadly.

Correct Answer: D

Rationale: RCTs (D) are experimental, not observational. A, B, and C observe natural events without intervention.