100+ Free FCPHM(SA) Part I Practice Questions

Explanation: Cumulative incidence measures the proportion of initially disease-free individuals who develop the disease over a specified period. The population at risk at the start of the year is 200,000 minus 500 existing cases = 199,500. Calculating 100 / 199,500 yields approximately 50.1 per 100,000 (or 50 per 100,000 population at risk). Existing cases are excluded from the denominator.

Explanation: When incidence rate and duration of disease are stable over time and prevalence is low (<10%), point prevalence is approximately equal to the product of incidence rate and average disease duration (P = I × D). This fundamental relationship demonstrates that increases in treatment survival (extending duration) increase prevalence even if incidence remains unchanged.

Explanation: Case fatality rate (CFR) is the proportion of persons diagnosed with a specific disease who die from that disease within a given timeframe. CFR = (Number of deaths from disease / Total diagnosed cases of disease) × 100 = (8 / 400) × 100 = 2.0%. A CFR below 1% is the target standard for managed cholera outbreaks according to WHO/NICD guidelines.

Explanation: Primary prevention aims to prevent the initial onset of disease by reducing exposure to hazards or enhancing individual resistance before disease pathology develops. Immunization via BCG vaccination at birth is a classic primary prevention intervention against severe childhood tuberculosis.

Explanation: Sensitivity is the proportion of truly diseased individuals who test positive: TP / (TP + FN). Here, TP = 100 and FN = 20, so Sensitivity = 100 / (100 + 20) = 100 / 120 = 83.3%.

Explanation: Specificity is the proportion of non-diseased individuals who receive a negative test result: TN / (TN + FP). Here, TN = 270 and FP = 30, giving Specificity = 270 / (270 + 30) = 270 / 300 = 90.0%.

Explanation: Positive Predictive Value (PPV) depends heavily on disease prevalence. As prevalence decreases, the absolute number of true positive cases falls while false positives (generated from the large pool of non-diseased people) relative to true positives increase. Consequently, PPV decreases markedly as disease prevalence declines.

Explanation: Category 1 Notifiable Medical Conditions (NMC) in South Africa are conditions of major public health concern that must be reported within 24 hours of identification to enable immediate outbreak response. Viral Haemorrhagic Fevers, cholera, rabies, plague, and acute flaccid paralysis are Category 1 NMCs.

Explanation: Passive surveillance relies on healthcare providers and laboratories routinely submitting reportable disease notifications to public health authorities without specific solicitation or active follow-up visits. It is lower cost but subject to underreporting.

Explanation: A point source outbreak occurs when individuals are exposed to a single, common vehicle of infection simultaneously over a brief duration (e.g. contaminated dish at a wedding feast). The epidemic curve shows a single rapid rise, a single peak matching one incubation period, and a steep decline.