Case Fatality Rate
Proportion of diagnosed individuals who die from the disease.
Formula
Variables
Example
50 deaths out of 2 500 cases → CFR = 2 %
How it works
The case fatality rate shows what fraction of people who have been diagnosed with a disease die from it. It is calculated by dividing the number of deaths caused by the disease by the number of confirmed cases, then multiplying by 100 to convert the fraction into a percentage. This works because it compares deaths to the total group at risk within the diagnosed cases, giving a simple measure of how severe the disease is in that group.
When to use it
Use this formula when analyzing how deadly a disease is among confirmed patients, such as during an outbreak or for a specific illness in a hospital or region. It is useful in public health reports, outbreak investigations, and comparing severity across diseases or time periods.
Worked example, step by step
Suppose a city reports 18 deaths from a disease among 900 confirmed cases. CFR = (Deaths / Confirmed Cases) × 100 CFR = (18 / 900) × 100 CFR = 0.02 × 100 CFR = 2% So, the case fatality rate is 2%.
Common mistakes to avoid
- Using all people exposed to the disease instead of only confirmed cases
- Forgetting to multiply by 100 when reporting the result as a percentage
- Counting deaths from other causes instead of deaths caused by the disease
Did You Know?
CFR can be misleading during an outbreak because many cases haven't yet resolved — the true rate often differs from early estimates.
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