Core antibodies and other parameters of hepatitis B virus infection in a tropical population.

HBsAg (80% of ay subtype) was detected with radioimmunoassay in 10% of a sample of the healthy population in Mopti, Mali, and in 6% with counterelectrophoresis. Anti-HBs was detected in approximately 57% of adults, and anti-HBc in 50%. Anti-HBs was not always detectable in anti-HBc positive sera with the methods used, and vice versa. This accounted for up to 85% of an adult group showing anti-HBs, anti-HBc, or both. While anti-HBc percentages climbed more gradually with age, and 'adult' percentage of anti-HBs was reached at about 3 years of age, and there were no significant differences in the age distribution of HBsAg.