You have to consider that European and Asian populations spent centuries building up resistance to various plagues that would quickly kill off a quarter of the

You have to consider that European and Asian populations spent centuries building up resistance to various plagues that would quickly kill off a quarter of the population. It’s hard to imagine what it would mean to have all those various infectious agents sprung on a new population all at once. https://en.m.wikipedia.org/wiki/List_of_epidemics https://en.m.wikipedia.org/wiki/List_of_epidemics