Prevalence of antibody to hepatitis A virus in Okinawa and Kyushu, Japan.

Between 1968 and 1981, a total of 1955 serum samples from healthy subjects chosen at random in seven districts of Okinawa and two districts of Kyushu were surveyed for antibody to hepatitis A virus (anti-HAV) by radioimmunoassay. Overall prevalence of anti-HAV was 55.1% in Okinawa and 35.9% in Kyushu. Prevalence of less than 10% was observed in subjects less than or equal to 14 years of age in Okinawa and less than or equal to 24 years of age in Kyushu. In three of the districts of Okinawa, second serum samples were collected after intervals of eight, 10, and 12 years, respectively. Overall prevalence of anti-HAV decreased significantly over these time periods. When the age-specific prevalence of anti-HAV on the first occasion is compared with that on the second occasion, it can be seen that there have been few new cases of hepatitis A infection. These data suggest that hepatitis A infection among children has declined dramatically in recent years, and that young people may be highly susceptible to hepatitis A virus.