To understand the possible origin and dissemination of HTLV-I infection in northeast Asia, community-based molecular epidemiological studies were conducted on the Kinmen Islands (off the coast of Fukien Province, China) and in Taiwan. A total of 3831 Taiwanese from 3 townships (Pu-Li, Chu-Dung, and Pu-Tze) and 993 aborigines from 4 tribes in Taiwan participated in this study. The prevalence rates of HTLV-I infection in adult residents from Pu- Li, Chu-Dung, and Pu-Tze were 0.82, 1.72, and 1.63%, respectively. None of the aborigines had HTLV-I infection. Previously, 0.73% of the adult population of Kin-Hu, Kinmen were found to have HTLV-I infection. Peripheral blood mononuclear cells were collected from HTLV-I carriers identified both in Taiwan and Kinmen and the HTLV-I LTR sequences were PCR amplified, subcloned, and sequenced for phylogenetic tree analysis. The results showed that all 6 HTLV-I isolates from Kinmen and 13 of 18 (72.2%) isolates from Taiwan were group a (transcontinental) of Cosmopolitan subtype, while 5 of 18 (27.8%) isolates from Taiwan were group b (Japanese) of Cosmopolitan subtype. Since all of the HTLV-I-infected persons were descendants of immigrants from mainland China, the origin of the Cosmopolitan subtype in Taiwan and Kinmen may not have been Japan, as previously theorized, but China, possibly the result of the migration of an infected population in the past several centuries.
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