In an outbreak of viral hemorrhagic fever in a village with a population of 20,000, 200 cases were reported and 25 deaths occurred. Calculate the case fatality rate?

1. A

   1.25%

2. B

   0.13%

3. C

   25%

4. D

   12.50%

Appeared in: Haryana CHO - 2022

Explanation

• The Case Fatality Rate (CFR) measures the proportion of deaths among confirmed cases of a disease.
• The formula for CFR is: (Number of deaths due to a disease / Total number of cases of the disease) × 100.
• In this scenario, there were 25 deaths among 200 reported cases.
• Plugging the values into the formula: (25 / 200) × 100 = 0.125 × 100 = 12.5%.
• The total population of 20,000 is irrelevant for calculating the CFR and is used for calculating the overall mortality rate.

Why Other Options Were Wrong

• Option A: This value (1.25%) would result from a calculation error, likely misplacing the decimal point, for instance, by dividing 25 by 2000 instead of 200.
• Option B: This value (0.13%) is the crude mortality rate for the entire population (25 deaths / 20,000 population = 0.00125 or 0.125%), not the case fatality rate. It incorrectly uses the total population as the denominator.
• Option C: This value (25%) is a miscalculation. It might be obtained by incorrectly simplifying the fraction, for example, by dividing 25 by 100 instead of 200.

Related Visual

Clinical Relevance

• Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Calculation of Case Fatality Rate (CFR) in an outbreak scenario as background academic context rather than a clinical decision trigger.
• Understanding CFR is crucial for nurses during an outbreak to assess the severity of the disease and anticipate the level of care and resources needed.
• During a VHF outbreak, nurses are on the front lines and must implement strict infection control protocols (e.g., use of PPE, patient isolation, safe waste disposal) due to the typically high CFR and risk of nosocomial transmission.
• Nurses play a key role in surveillance, reporting new cases and deaths accurately, which is essential for calculating real-time CFR and guiding public health responses.

How to Approach the Question

• First, identify the specific epidemiological measure the question asks for, which is the 'case fatality rate'.
• Recall the correct formula for this measure: CFR = (Number of Deaths / Number of Cases) × 100.
• Carefully read the problem to extract the necessary values: Number of deaths = 25, Number of cases = 200.
• Identify any distractor information that is not needed for the formula. In this case, the total population of 20,000 is a distractor for calculating CFR.
• Substitute the correct values into the formula: (25 / 200) × 100.
• Perform the calculation and compare the result (12.5%) with the given options to find the correct answer.

Concept Tested & Keywords

• Concept Tested: Calculation of Case Fatality Rate (CFR) in an outbreak scenario.
• Stem keywords: viral hemorrhagic fever, outbreak, population, cases, deaths, case fatality rate
• Lead-in keywords: Calculate
• Clinical cues: The question provides total population, number of cases, and number of deaths, requiring the correct selection of data for the specific formula.

Question ID

QRkuFyB7sm1dOKlNKgxabf

Copy ID

Reference Book

E6 Medicine Harrison 22e Part 1 p. 1722-1724

E6 Nelson Textbook of Pediatrics(2024) — Volume 1 p. 2080-2082