Essay on Hepatitis B

This essay has a total of 1390 words and 8 pages.

Hepatitis B


Risk Factors for HBV Infection

Although relatively rare in the United States, hepatitis B is endemic in parts of Asia
where hundreds of millions of individuals may be infected. HBV is transmitted horizontally
by blood and blood products and sexual transmission. It is also transmitted vertically
from mother to infant in the perinatal period which is a major mode of transmission in
regions where hepatitis B is endemic.


The blood supply in developed countries has been screened for HBV for many years and at
present transmission by blood transfusion is extremely rare. Major routes of transmission
among adults in Western countries are intravenous drug use and sexual contact. The risk of
HBV infection is notably high in promiscuous homosexual men but it is also transmitted
sexually from men to women and women to men. Transmission is probably prevented by correct
use of condoms. Health care workers and patients receiving hemodialysis are also at
increased risk of infection.


Effective vaccines are available for the prevention of HBV infection. All individuals at
risk for infection should be vaccinated. Post-exposure prophylaxis with hepatitis B immune
globulin is also effective for non-immune individuals after a known exposure (e. g. needle
stick).




Consequences of HBV Infection

HBV causes acute and chronic hepatitis. The chances of becoming chronically infected
depends upon age. About 90% of infected neonates and 50% of infected young children will
become chronically infected. In contrast, only about 5% to 10% of immunocompetent adults
infected with HBV develop chronic hepatitis B. In some individuals who become chronically
infected, especially neonates and children, the acute infection will not be clinically
apparent.


Acute hepatitis B can range from subclinical disease to fulminant hepatic failure in about
2% of cases. Many acutely infected individuals develop clinically apparent acute hepatitis
with loss of appetite, nausea, vomiting, fever, abdominal pain and jaundice. In cases of
fulminant hepatic failure from acute HBV infection, orthotopic liver transplantation can
be life-saving. About 90% to 95% of acutely infected adults recover without sequelae.
About 5% to 10% of acutely infected adults become chronically infected.


The natural history of chronic HBV infection can vary dramatically between individuals.
Some will develop a condition commonly referred to as a chronic carrier state. These
patients, who are still potentially infectious, have no symptoms and no abnormalities on
laboratory testing. Nonetheless, some of these patients will have evidence of hepatitis on
liver biopsy.


Some individuals with chronic hepatitis B will have clinically insignificant or minimal
liver disease and never develop complications. Others will have clinically apparent
chronic hepatitis. Some will go on to develop cirrhosis. Individuals with chronic
hepatitis B, especially those with cirrhosis but even so-called chronic carriers, are at
an increased risk of developing hepatocellular carcinoma (primary liver cancer). Although
this type of cancer is relatively rare in the United States, it is the leading cause of
cancer death in the world, primarily because HBV infection is endemic in the East.




Chronic infection with HBV can be either "replicative" or "non-replicative." In
non-replicative infection, the rate of viral replication in the liver is low and serum HBV
DNA concentration is generally low and hepatitis Be antigen (HBeAg) is not detected. HBeAg
is an alternatively processed protein of the pre-core gene that is only synthesized under
conditions of high viral replication. In "replicative" infection, the patient usually has
a relatively high serum concentration of viral DNA and detectable HBeAg. Patients with
chronic hepatitis B and "replicative" infection defined by the presence of detectable
HBeAg have a generally worse prognosis and a greater chance of developing cirrhosis and/or
hepatocellular carcinoma than those without HBeAg. In rare strains of HBV with mutations
in the pre-core gene, "replicative" infection can occur in the absence of detectable serum
HBeAg.




Diagnosis

The diagnosis of HBV infection is generally made on the basis of serology. Virtually all
individuals infected with HBV, either acutely or chronically, will have detectable serum
hepatitis B surface antigen (HBsAg). In acute infection, HBsAg is detectable several weeks
after infection and its appearance coincides with the onset of clinical symptoms. HBeAg is
also detectable in acute infection which is characterized by a high rate of viral
replication. At around the same time, IgM antibodies against core antigen are detectable
in serum. Subsequently, IgG antibodies against core are produced. As acute infection
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