NavList:

Frank wrote:

From my point of view, the biggest problem with any of these supposed pre-Columbian sea voyages to the New World, whether from Europe or the Near East or China, is the total lack of immunity to Eur-asian diseases among Native Americans which became tragically obvious shortly after the first Spanish voyages to the Americas. So unless those voyages took place many centuries earlier, when the complex of deadly diseases would have been significantly different (e.g. no "black death" in Europe before about 1347), or unless the voyagers who took those early pre-Columbian voyages were astoundingly disease-free (which is possible with small isolated groups, like the Norse in Newfoundland), plague, smallpox and the rest should have been common in the Americas well before 1500.

 

Hang on a moment!  By their own accounts, the contact was typically brief, ephemeral, and hardly conducive to the transmission of diseases (helps to get up-close and personal for this).  Assuming that the voyagers were sick to begin with.  Nothing like a long sea voyage as a useful spell of quarantine.  Specifically I cite the accounts of early Scandinavian settlers in the north-east of North America, and early Spanish forays into southern parts of North America, etc.  They typically had little enough to do with the locals, apart from fighting with them when unavoidable.  As to the others - who knows!