Diseases of the Silk Road

Nature has twopapers out about something called "Behçet's disease." It has apparently also been termed the "Silk Road Disease", because of its associations with populations connected to the Central Eurasian trade networks.Though described by Hippocrates 2,500 years ago, apparently it was "discovered" only in the 20th century by a Turkish physician. The reason that that might be is obvious; the prevalence of Behçet's disease is far higher in Turkey than any other nation. Two orders of magnitude difference between Northwest Europeans and Turks. East Asian populations are somewhere between Europeans and Turks, while the coverage of Inner Asia itself is thin (the first case diagnosed in Mongolia was in 2003). Additionally, the relatively similar frequency in Morocco and Iran, despite the latter nation being strong influenced by Turkic migration (25-30% of Iranian citizens are ethnically Turk), and the former not at all, leads to me wonder if there may be convergence or parallelism, rather than common ancestry, at work (or, more likely, a combination of both). The relationship between Morocco and Japan to the Silk Road in a direct fashion is tenuous at best. These were two polities which managed to be just outside the maximum expanse of Turanian empires. The Japanese famously repulsed the Mongol invasion ordered by Kublai Khan, while the Arab rulers of Morocco never fell under Ottoman control.And the early documentation by Hippocrates makes me wonder at the frequency of the disease in Greece itself. Greeks presumably contributed to the ancestry of modern Anatolian Turks, but it is far less likely because of the nature of the Ottoman system that Turks would have contributed to the ancestry of Greeks. I can't find prevalence data for Greece, but it may be an open question in what direction the disease spread along the Silk Road.