It appears before onset of symptoms, peaks during overt disease, and then declines to undetectable levels in 3 to 6 months. Persistence beyond 6 months indicates continued 36
viral replication, infectivity, and chronic hepatitis. HBeAg appears in the serum soon after HBsAg and signifies active viral replication. IgM anti-HBc becomes detectable shortly before the onset of symptoms, concurrent with the onset of an elevation in serum transaminases. Over the months, the IgM antibody is replaced by IgG anti-HBc. Anti-HBe is detectable shortly after the disappearance of HBeAg and its appearance signals the onset of resolution of the acute illness. IgG anti-HBs, a specific antibody to HBsAg, occurs in most individuals after clearance of HBsAg. Development of anti-HBs signals recovery from HBV infection, noninfectivity, and protection from future HBV infection. Anti-HBs is the antibody present in persons who have been successfully immunized against HBV.The presence of viral DNA (HBV DNA) in the serum is the most reliable indicator of HBV infection. It is transiently present during the presymptomatic period and for a brief time during the acute illness. The presence of DNA polymerase, the enzyme used in viral replication, usually is transient but may persist for years in persons who are chronically infected.Hepatitis B can be prevented by vaccination and by the screening of donor blood, organs, and tissues. The vaccine, which is prepared from purified HBsAg produced in yeast, induces a protective antibody response in 95% of vaccinated infants, children, and adolescents.3The CDC recommends vaccination of all children 0 to 18 years of ageas a means of preventing HBV transmission.12The vaccine also is recommended for all unvaccinated adults who are at high risk for infection, international travelers to regions with high or intermediate levels of endemic HBV infection, persons with human immunodeficiency virus (HIV) infection, persons with chronic liver disease, injection drug users, and all other persons seeking protection.12It is also recommendedthat all pregnant women be routinely tested for HBsAg during an early prenatal visit and that infants born to HBsAg-positive mothers receive appropriate doses of hepatitis B immune globulin (HBIG) and hepatitis B vaccine.9Hepatitis CThe hepatitis C virus, discovered in 1989, is a member of the Flaviviridaefamily. It is a small, enveloped, single-stranded RNA virus.3,4The virus is genetically unstable, giving rise to multiple genotypes and subtypes. This allows a divergent population of closely related variants to circulate in infected persons.3One of the HCV envelope proteins, the E2 protein, which is the target for anti-HCV antibodies, is the most variable region of the entire viral genome. It is likely that the wide diversity of genotypes contributes to the pathogenicity of the virus, allowing it to escape the actions of host immune mechanisms and antiviral medications, and to difficulties in developing a preventive vaccine.