Characteristic regional prevalence of HTLV-I in Shimane Prefecture.

Serological survey for human T-lymphotropic virus type I (HTLV-I) was performed in Shimane Prefecture, Japan, located on the coast of Japan sea. The rates of anti-adult T-cell leukemia-associated antigen-positive sera were 4.2% and 6.9% respectively for males and females. The rate increased with age, particularly in females. From the geographical point of view, the Oki Islands and a very small focus in Shimane-cho had high rates of anti-adult T-cell leukemia-associated antigen positives. Even within the Oki Islands, there was a big difference in the rate of seropositives between Dozen and Dogo which are only 10 km apart. The focus, Shimane-cho, has a population of 299. Even within a small area, there is a tendency of HTLV-I carriers to form a very narrow focus.