Observation of a cohort participant stops at one of four end points. Which event is not one of them?

1. Person-time accrues from an established starting time until one of four end points is reached. 2. Those four are onset of disease, death, migration out of the study, and the end of the study itself. 3. Migration out is recorded as loss to follow-up, so it closes a participant's contribution. 4. Recovery from some other illness leaves the participant still at risk and still under observation, so it ends nothing. _Source: CDC Principles of Epidemiology in Public Health Practice (3rd ed., US federal, public domain), Lesson 3 "Measures of Risk", section Definition of incidence rate_