Many of the crew members who served on this voyage later joined the army of King Charles VIII in his invasion of Italy in 1495, resulting in the spreading of the disease across Europe and as many as five million deaths.
The findings suggested Europeans could have carried the nonvenereal tropical bacteria home, where the organisms may have mutated into a more deadly form in the different conditions and low immunity of the population of Europe.
although this is only possible if syphilis existed in the Old World prior to Columbus (see § Origin).Despite the tradition of assigning the homeland of yaws to sub-Saharan Africa, Crosby notes that there is no unequivocal evidence of any related disease having been present in pre-Columbian Europe, Africa, or Asia.Crosby writes, "It is not impossible that the organisms causing treponematosis arrived from America in the 1490s ...[...] As in all scientific fields, in order to resolve the controversy over the origin and antiquity of syphilis in the Old World, there is a strong need for adherence to standard practice in scientific publication and the increased publication of relevant evidence in peer-reviewed journals." The theory holds that syphilis was present in Europe before the arrival of Europeans in the Americas.Some scholars during the 18th and 19th centuries believed that the symptoms of syphilis in its tertiary form were described by Hippocrates in Classical Greece. Owsley, a physical anthropologist at the Smithsonian Institution, and other supporters of this idea, say that many medieval European cases of leprosy, colloquially called lepra, were actually cases of syphilis.