> it is estimated that 90% of new world natives died of smallpox and viral herpes immediately following contact with europeans

Can you give an academic citation for this?

I can't find anything that would support these numbers, they're high even for older work that's since been debunked (and especially not "immediately"). I suspect that there's a methodological error, but I can't say for certain until I actually see how you've come to these numbers.