Community and Public Health Nursing
This domain tests population-level reasoning: measuring disease, choosing prevention, running immunization and screening, and reporting notifiable diseases through Mongolia's soum-aimag-national structure. Zoonoses and winter air pollution are distinctive local content.
Core rules
- Incidence counts new cases per population at risk per unit time; prevalence counts all existing cases at a point. Screening affects prevalence, not incidence.
- Sensitivity is the proportion of diseased people who test positive; specificity is the proportion of healthy people who test negative. Positive predictive value depends on prevalence.
- Prevention levels: primary (immunization, clean water, tobacco control), secondary (screening, TB case-finding, cervical cytology), tertiary (rehabilitation, chronic disease self-management).
- Notifiable diseases must be reported promptly through the local reporting chain; speed matters most for plague, anthrax, rabies exposure and measles.
- Local zoonoses: brucellosis in herders with fever and arthralgia after livestock contact or unpasteurized milk; tick-borne rickettsiosis in spring; echinococcosis linked to dogs; rabies after dog bites.
- Cold chain: vaccines held at 2-8 C, monitored with a vaccine vial monitor; hepatitis B and pentavalent vaccines must never be frozen.
Worked example
Screening 10,000 people where prevalence is 2%: 200 have the disease. With 90% sensitivity, 180 are true positives. With 95% specificity among the 9,800 healthy, 490 are false positives. PPV = 180 / (180 + 490) = 27%. Reasoning: even a good test in a low-prevalence population mostly finds healthy people, so every positive needs confirmation before treatment or disclosure.
Traps
Using the whole population instead of the population at risk; claiming screening diagnoses disease; forgetting that PPV falls when prevalence falls; freezing hepatitis B vaccine; reporting a notifiable disease only at month end.