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Case Fatality Rate (CFR) Calculator

Proportion of deaths among confirmed cases.

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CFR

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Overview

The Case Fatality Rate (CFR) measures the proportion of individuals diagnosed with a specific disease who die from that disease within a specified period. It serves as a critical metric in epidemiology to characterize disease severity and the quality of clinical management during an outbreak.

Symbols

Variables

D = Deaths, C = Cases, CFR = CFR

Deaths
Variable
Cases
Variable
CFR
CFR
%

Apply it well

When To Use

When to use: Apply this formula when you have a defined group of confirmed medical cases and need to calculate the probability of death among those diagnosed. It is most accurate when an outbreak has concluded and all outcomes—recovery or death—are finalized.

Why it matters: CFR helps public health officials assess the virulence of a pathogen and the effectiveness of healthcare systems. By comparing CFRs across different regions or demographics, researchers can identify high-risk populations and allocate life-saving resources more efficiently.

Avoid these traps

Common Mistakes

  • Using entire population as denominator instead of confirmed cases.
  • Convert units and scales before substituting, especially when the inputs mix %.
  • Interpret the answer with its unit and context; a percentage, rate, ratio, and physical quantity do not mean the same thing.

One free problem

Practice Problem

During a localized outbreak of a new influenza strain, health officials recorded 2,500 confirmed cases and 50 deaths. What is the Case Fatality Rate for this outbreak?

Cases2500
Deaths50

Solve for: cfr

Hint: Divide the number of deaths by the number of confirmed cases, then multiply by 100 to get the percentage.

The full worked solution stays in the interactive walkthrough.

References

Sources

  1. Gordis, L. (2014). Epidemiology (5th ed.). Elsevier Saunders.
  2. World Health Organization. (n.d.). Case fatality ratio (CFR). Retrieved from https://www.who.int/data/gho/data/indicators/indicator-details
  3. Wikipedia: Case fatality rate
  4. Centers for Disease Control and Prevention. Principles of Epidemiology in Public Health Practice, Third Edition.
  5. Gordis L. Epidemiology. 6th ed. Elsevier; 2019.
  6. Centers for Disease Control and Prevention (CDC). Principles of Epidemiology in Public Health Practice, Third Edition.
  7. World Health Organization (WHO). A guide to the estimation of the burden of foodborne diseases. Chapter 2: Measuring disease occurrence.
  8. GCSE Medicine & Healthcare — Epidemiology