Seroepidemiology of viral hepatitis: correlation with clinical findings.

Antibody to hepatitis A antigen (anti-HA) is detectable in the serum shortly after infection with hepatitis A virus. The presence of IgM antibody indicates acute infection; IgG signifies past infection. Hepatitis B surface antigen (HBsAg) indicates infectiousness and is usually present when hepatitis B virus causes active liver disease; its antibody (anti-HBs) is neutralizing and confers immunity. Antibody to core antigen (anti-HBc) is an index of hepatitis B viral replication when present in high titers; in low titers it reflects past infection. Early presence of e antigen (HBeAg) indicates a high degree of infectivity, whereas presence of its antibody (anti-HBe) indicates a lesser degree. Although markers of non-A non-B hepatitis have been described, the definitive nature and number of the virus or viruses are not yet clear.