Why did the u. s. delay entry to world war i until 1917?
the u. s. was not industrialized enough to compete with european powers.
the u. s. had previously held a policy of isolationism.
the u. s. was concerned about unrestricted submarine warfare.
the u. s. had alliances with both germany and great britain.

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.