It would seem that metabolic rates would be higher in monkeys than humans, and that monkeys might show symptoms earlier.
Perhaps.
I might propose alternately, that ebola and monkeys have been around far longer and it’s figured out monkeys more efficiently than it has humans. So far. It’s throwing genetic spaghetti at the wall in the current outbreak with the H2H2H2H...transmission chain so who knows what sort of mutations will enable it to do the same with us, ultimately.