EG-R023 | Attack Rate Calculator

Calculate outbreak attack rate from new cases and the exposed or at-risk population, with automatic interpretation.

1. Enter data

Measure type

Report per

New cases during outbreak / exposure period

Population at risk / exposed population

Disease / event label

Place / group assessed

Outbreak / exposure period

Attack rate

—

Per multiplier

—

95% confidence interval

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Enter data and calculate to generate an interpretation.

Indicative level: —

Use a denominator that truly represents the exposed or at-risk population.
Apply the same case definition to all cases included in the numerator.
Record the outbreak/exposure period and the source of the denominator.
For food-specific analysis, calculate attack rates separately for exposed and non-exposed groups.
Small denominators can produce unstable percentages; interpret the confidence interval.