Hepatitis B (cont.)
How is the hepatitis B virus spread (transmitted)?
Hepatitis B is spread mainly by exposure to infected blood or body
secretions. In infected individuals, the virus can be found in the blood,
semen, vaginal
discharge, breast milk, and saliva. Hepatitis B is not spread through
food, water, or by casual contact.
In the United States, sexual contact is the most common
means of transmission, followed by using contaminated needles for injecting
illicit drugs, tattooing, body piercing, or acupuncture. Additionally, hepatitis B can
be transmitted through sharing toothbrushes and razors contaminated with
infected fluids or blood.
Hepatitis B also may be spread from infected mothers to their babies at birth
(so-called 'vertical' transmission). This is the most prevalent means of
transmission in regions of the world where hepatitis B rates are high. The rate
of transmission of hepatitis B from mother to newborn is very high, and almost
all infected infants will develop chronic hepatitis B. Fortunately, transmission
can be significantly reduced through immunoprophylaxis (see below).
Rarely, hepatitis B can be transmitted through transfused
blood products, donated livers and other organs. However, blood and organ donors are routinely
screened for hepatitis which typically prevents this type of transmission.
What are the symptoms of acute hepatitis B?
Acute hepatitis B is the period of illness that occurs
during the first one to four months after acquiring the virus. Only 30% to 50% of adults
develop significant symptoms during acute infection. Early symptoms may be
non-specific, including fever, a flu-like illness, and joint pains. Symptoms of
acute hepatitis may include:
Rarely, acute hepatitis damages the liver so badly it can
no longer function. This life-threatening condition is called "fulminant
hepatitis." Patients with fulminant hepatitis are at risk of developing bleeding
problems and coma
resulting from the failure of the liver. Patients with fulminant hepatitis
should be evaluated for liver transplantation. Small studies suggest that the
drug lamivudine (Epivir), may be of limited assistance in these cases (see
below).
What determines the outcome of acute hepatitis B?
The body's immune response is the major determinant of
the outcome in acute hepatitis B. Individuals who develop a strong immune
response to the infection are more likely to clear the virus and recover.
However, these patients also are more likely to develop more severe liver injury
and symptoms due to the strong immune response that is trying to eliminate the
virus. On the other hand, a weaker immune response results in less liver injury
and fewer symptoms but a higher risk of developing chronic hepatitis B. People
who recover and eliminate the virus will develop life-long immunity, that is, protection from subsequent
infection from hepatitis B.
Most infants and children who acquire acute hepatitis B
viral infection have no symptoms. In these individuals, the immune system fails
to mount a vigorous response to the virus. Consequently, the risk of an infected
infant developing chronic hepatitis B is greater than 95%. In contrast, only 5% of adults who have
acute hepatitis B develop chronic hepatitis B.
Next: What are the symptoms of chronic hepatitis B infection? »
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