Community and Public Health: Populations, Prevention, and Programs
Public health questions test your ability to think at the population level. Understand the core functions: assessment, policy development, and assurance. Know the levels of prevention - primary (immunization, health education), secondary (screening, early detection), and tertiary (rehabilitation, limiting disability). Be fluent in study designs: cohort studies measure incidence and relative risk, case-control studies measure odds ratios and suit rare outcomes, and randomized trials establish causality.
Epidemiology essentials
Calculate and interpret incidence, prevalence, sensitivity, specificity, positive predictive value, and attributable risk. Remember that positive predictive value rises with prevalence, which is why screening programs target high-risk groups. Outbreak investigation follows steps: verify the diagnosis, define and find cases, describe by person, place, and time, generate hypotheses, and implement control.
Health systems and Afghanistan context
Community health worker programs, basic health packages, and maternal-child health priorities are common themes. Know the importance of cold chain for vaccines, water and sanitation for diarrheal disease control, and directly observed therapy for tuberculosis.
Traps
Distinguish incidence from prevalence, and sensitivity from predictive value. A highly sensitive test is good for ruling out disease; a highly specific test confirms it.
Rule of thumb
Use the 2x2 table: sensitivity = true positives divided by all diseased; specificity = true negatives divided by all non-diseased. Draw the table before answering.