To be considered a primary source, a source must be:

a. written or created by an educated expert.
b. written or created by a person who experienced an event.
c. written or created for use as historical evidence.
d. written or created by an objective, unbiased person.

B)written or created by a person who experienced an event.

The constant presence of diseases or infectious agents within a given geographic area or population group. it may also refer to the usual prevalence of a given disease with such area or group. it includes holoendemic and hyperendemic diseases. a holoendemic disease is one for which a high prevalent level of infection begins early in life and affects most of the child population, leading to a state of equilibrium such that the adult population shows evidence of the disease much less commonly than do children (malaria in many communities is a holoendemic disease). a hyperendemic disease is one that is constantly present at a high incidence and/or prevalence rate and affects all groups equally. so probably family history.