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.
3
The CDC recommends vaccination of all children 0 to 18 years of age
as a means of preventing HBV transmission.
12
The 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.
12
It is also recommended
that 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.
9
Hepatitis C
The hepatitis C virus, discovered in 1989, is a member of the
Flaviviridae
family. It is
a small, enveloped, single-stranded RNA virus.
3
,
4
The 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.
3
One 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.
