The presence of leprosy in China is documented to 190 BC, and possibly earlier.; It is believed to have spread from China to Japan. Its presence in Oceania has heretofore been documented only since the eighteenth and nineteenth centuries AD, and has been attributed to migration of people from China into the Pacific subsequent to western contact and trans-Pacific trade.
In the osteological analysis of 700 skeletons from pre-Spanish archaeological contexts on the islands of Guam and Saipan in western Micronesia, at least six cases of leprosy have been discovered. Radiocarbon dating places two of these in the thirteenth to fifteenth centuries AD, one in the eleventh to thirteenth centuries, and one in the seventh to eleventh centuries. This clearly indicates that the introduction of leprosy pre-dates western contact and suggests possible contact with, or immigration from, China or Japan.