Massive sero-epidemiological survey of hepatitis C virus: clustering of carriers on the southwest coast of Tsushima, Japan.

We conducted a mass screening survey for anti-hepatitis C virus antibody (anti-HCV-Ab) among 1,009 inhabitants, 341 males and 668 females, older than 40 years, in south Tsushima in 1989. The overall positive rate for anti-HCV-Ab was 2.3% (2.9% in males and 1.9% in females). The positive rate for anti-HCV-Ab among people with histories of blood transfusions was 14.8% (8/54), which was higher than than (1.6%, 15/955) in people without blood transfusions (P less 0.001). The positive rate (15.1%, 8/53) in people with an elevated level of glutamic oxalacetic transaminase (GOT, greater than or equal to 41 U/liter) or glutamic pyruvic transaminase (GPT, greater than or equal to 36 U/liter) was significantly higher than that (1.6%, 15/956) for people with normal values of GOT and GPT (P less than 0.001). The most interesting finding was that the anti-HCV-Ab positives without histories of blood transfusions were clustered in a few villages located in the southwestern coastal areas of Tsushima, where the positive rate of 3.7% (13/355) was significantly higher (P less than 0.001) than that of 0.3% (2/600) in other villages.