this might be a little off topic but I've heard (in school) that when we invaded the native americans a ton of them got sick from us.. it doesn't make sense to me that now people fly here from china, england, africa, everywhere on planes carrying who knows what, yet there aren't widespread epidemics happening 24/7. of course some people might associate this with vaccines, or maybe the babies are just born immune these days (i don't know if that's possible), but what is the reason we aren't getting sick like the native americans from the widespread contact of humans all around the globe, if it's not vaccines doing?