It is reasonable to hypothesize that during the mexican-american war (1846-1848) when some irish soldiers deserted from the u. s. army to join the mexican army instead, most were at least partly motivated by

Feelings of loyalty toward fellow roman catholics
(i think that's the right answer)

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.