Which of the following is a primary activity of epidemiology?

• A. Diagnosing individual patients
• B. Prescribing medication
• C. Performing surgeries
• D. Comparing disease rates between populations

Answer: (D)

Epidemiology focuses on how disease affects groups, looking at patterns, distributions, and determinants across populations rather than treating individual patients. The best choice reflects this: comparing disease rates between populations allows us to measure incidence and prevalence, identify disparities or trends, and evaluate how risk factors or interventions influence health at the population level. This is the core way epidemiologists learn what’s happening in communities and how to guide public health actions.

Diagnosing individual patients, prescribing medications, and performing surgeries are clinical activities aimed at the care of a single person, not at analyzing disease patterns across groups.