Prevalence of a human retrovirus in native Japanese: evidence for a possible ancient origin.

The origin of a human retrovirus (ATLV or HTLV-I) is, at present, unknown although carriers of the virus have been found in Japan, the Caribbean basin and Africa. By means of a sero-epidemiological study, the Ainu people of Hokkaido, located in the northernmost island of Japan, were shown to have antibody to the virus in high frequency. Since the Ainu are regarded as descendants of the pre-agriculture native population of northern Japan, this finding appears to indicate that the retrovirus was already present in the aboriginal Japanese of prehistoric times.