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A hepatitis A epidemic produced 555 cases and 3 of the case-patients died. What is the case-fatality rate?
A54.1%
B5.4%
C0.5%
D0.1%
Answer & Solution
Correct answer: C. 0.5%
1. The case-fatality rate divides deaths among cases by the number of cases.
2. 3 divided by 555 equals 0.0054.
3. Multiplying by 100 gives 0.5%.
4. 5.4% and 54.1% slip the decimal point one and two places, the commonest error on small case-fatality figures.
5. 0.1% understates the same division by a further factor of five, so it too misreports a correct fraction.
_Source: CDC Principles of Epidemiology in Public Health Practice (3rd ed., US federal, public domain), Lesson 3 "Measures of Risk", section Case-fatality rate_
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