Translations:Advanced Field Epi:Manual 1 - Disease Investigation/32/en

For open populations (animal movement in or out) we need to adjust the denominator to take movements into account. Again the simplest way to do this is often to add half the number of animals that were added to the population at risk during the period and subtract half the number that left the population at risk, using the same approach as method 2 described above for cumulative incidence. The adjusted number is then multiplied by the length of the follow-up period.