Obviously the Mayans/Aztecs did not go to the Old World in massive numbers but were there any diseases passed to the Spaniards? Why were they not wiped out by new diseases as well? I’m sure there were some but I have never heard anything. Could these not have been brought back to Europe as well? Did they not survive the voyage?
It just seems odd to me that they were totally wiped out by diseases in their homeland when the Spaniards traveling vast distances with much less resources were able to stay healthy enough to conquer them.
It's generally accepted the Spanish europeans brought smallpox, measles, typhus, and cholera to the Americas while taking syphilis back with them.
Syphilis while not as deadly had a widely destabilizing effects on late Renaissance european society. The disease spread quickly through the noblity in particular creating a number of succession crisis' and wider unrest that fueled the reformation.
As an example Henry the VIII almost certainly suffered from the disease. His only "legitimate" son Edward the VI almost certainly suffered from congenital syphilis which lead to his early death at just 16. Henry's infertility and late life extermly unpredictable personality are mostly directly attributiable to his syphilis.
In addition to crediting the creation of the Church of England to the disease William McNeill in his book "Plagues and Peoples" suggests that the political decline of the Valois and Osman dynastys in France and Ottoman Turkey respectively was due to the disease as well.