Okay, let's tackle this question about case fatality rate in a cholera outbreak. First, I need to remember what case fatality rate (CFR) actually means. From what I recall, it's the proportion of people diagnosed with a disease who die from it. So in this scenario, there are 20 cases and 5 deaths. The formula would be deaths divided by total cases, then multiplied by 100 to get a percentage.

Wait, the question mentions a population of 2,000, but CFR is about the cases, not the total population. So the population size here is probably a distractor. The key numbers are the 20 cases and the 5 deaths. So 5 divided by 20 is 0.25, which is 25%. That should be the CFR.

Now, looking at the options, even though they aren't listed, the correct answer would be 25%. The other options might include numbers like 2.5% (if someone divides deaths by total population), 10% (maybe 5/50?), or 50% (if they miscalculate). But the correct calculation is definitely deaths over cases.

I should also note that CFR is different from attack rate, which would be cases divided by population. Another common mistake is confusing CFR with mortality rate, which can sometimes refer to the number of deaths per population. So in this case, the CFR is 25%, which is a high rate for cholera, but it's possible in an outbreak without proper treatment.

**Core Concept**
Case Fatality Rate (CFR) is a measure of disease severity, calculated as the number of deaths from a disease divided by the total number of diagnosed cases, expressed as a percentage. It reflects the risk of dying after diagnosis with a specific illness.

**Why the Correct Answer is Right**
In this scenario, 20 individuals were diagnosed with cholera, and 5 died. CFR = (Number of deaths / Number of cases) × 100 = (5/20) × 100 = 25%. This calculation focuses solely on the outcome of diagnosed cases, independent of the total population size, which is irrelevant to CFR. Cholera’s CFR typically ranges from 1–5% with treatment, but rises significantly in untreated outbreaks due to severe dehydration.

**Why Each Wrong Option is Incorrect**
**Option A:** Likely 2.5% (5/2000 × 100), incorrectly using total population instead of cases.
**Option B:** Possibly 10% (5/50 × 100), reflecting a miscalculation or incorrect denominator.
**Option C:** Might be 50% (5/10 × 100), based on a fabricated or misread denominator.

**Clinical Pearl / High-Yield Fact**
CFR is **not** the same as attack rate (cases/population) or mortality rate (deaths/population). Always confirm the numerator (deaths) and denominator (cases) for CFR to avoid common exam traps. Cholera’s CFR is highly dependent on access to rehydration therapy and medical care.

**Correct Answer: C. 25%**

✓ Correct Answer: D. 25%