an article on syphillis.
I'm too fuzzy minded to read it now, but the historical tracing of the epidemic from Columbus' sailors to Italy to the soldiers of Charles via the lovely Napolian ladies is pretty clear.
True, there may have been isolated cases before then, but given the promiscuity of the medieval days one does wonder why no one noticed it.
On the other hand, syphillis is related to yaws, which used to be common in Africa and spread by ordinanry skin contact. No, I've never seen a case. But early syphillis was a lot more virulent in the first hundred or so years it was in Europe, and could be spread by fairly innocuous ways like kissing (not deep kissing, but the cheek to cheek contact common those days when one greeted another, presumably via saliva containing germs and open skin...a few cases of HIV have been spread this way).
So is it new or old or just mutated?
More recently, Zuckerman was also part of a team that published a 2011 paper in the Yearbook of Physical Anthropology reviewing 54 different reports of treponemal disease in pre-Columbian Europe. None of the cases, they argued, presented evidence strong enough—either in the dating of the bodies or the signs of syphilis they displayed— to validate the pre-Columbian hypothesis.
and remember: They have found female DNA in a few people in Norway.
And of course, the cod fishermen would fish off the coast of Canada, so presumably could have visited the lovely ladies there.
Or did the Mali navy who got blown off course to Brazil catch it and bring it to Africa, or maybe they took yaws to Brazil? Remember, the "pristine rain forest" of the Amazon was very populated in those days with millions of farmers.
finally, even a rare case in China or Japan might have managed to get there via polynesians or just sailors who got blown off course.
The presence of African sweet potatoes in Polynesia sugggests that there were some contacts.