I think the number killed by Old World diseases is overstated. Case in point, what was widely thought mostly Old World diseases turned out to be indigenous hemorrhagic fevers that killed large swaths of Meso-America in the 16th century.
No, I don’t think that’s been “proven” at all.
Smallpox, measles, influenza, malaria, cholera, typhoid and even corona and rhinovirus all took their toll.
Now I have read that SOME are proposing the plagues in early New Spain (Central Mexico today) were hemorrhagic fevers but that was a localized event only and did not spread north or south, and certainly NOT to the lands that would become the USA and Canada, or South America and the Caribbean.