First, it was a two-way street. Syphilis, for one, is believed to have originated in the new world and have been brought to Europe post-contact.
But Europe, Asia, and Africa combined was a much bigger population pool, so more opportunities for mutation and transmission leading to more types of infectious diseases.
But Europe, Asia, and Africa combined was a much bigger population pool, so more opportunities for mutation and transmission leading to more types of infectious diseases.