[Seven plus One]

...That one doggone near erradicated humanity from the Americas!

Are you referring to this?

[muawiyah]

Yup. There was a similar occurrence in the Andes, and by the time white folk traversed the big swamps in the middle of South America on their way East to the coast virtually all the native people had died in a massive calamity, presumably plague.

There's a couple of recent books about that trip. Try Gaspar de Carvajal.