Bout time they start talking about the pre-pilgrim plague.
I don't think the pre pilgrim plague was the first or the worst either. No rational person can look at the evidence and believe that tribes of a few dozen individual hunter gatherers did some of the things they did. To build a place like Cahokia took thousands of settled people many years to build.
I think there were lots of visitors over the years who brought a lot of diseases with them. Western Europeans were just the first to successfully settle.
One very interesting book is “Guns Germs and Steel” by Jared Diamond.
He suggests that the old world is oriented east-west, permitting agricultural technologies to migrate easily, while the new world is oriented north-south, so agricutural technologies would have to cross hostile climate bands.
Because of that the old world had superior domestic animals, and superior diseases in their domestic animals to which the native Americans had no resistance. Smallpox (from cattle) gets the press, but probably measles (from Rinderpest in cattle), typhus(perhaps American in origin), plague (from rats) and influenza (from swine) all played a part.