Cumulative incidence is the incidence calculated using a period of time during which all of the individuals in the population are considered to be at risk for the outcome. It is sometimes referred to as the incidence proportion or the attack rate.

Cumulative incidence is calculated by the number of new cases during a period divided by the number of people at risk in the population at the beginning of the study.

It may also be calculated by the incidence rate multiplied by duration.

$CI(t)=1-e^\{-IR(t)\; *\; D\},$

See also

• OpenEpi software program