Hepatitis B is a worldwide health problem. It is transmitted via various methods as discussed below. The primary mechanisms of transmission are sexual and from mother to fetus at child birth. When HBV is acquired at these early times in life, chronic hepatitis B develops in approximately 100 % cases. The transmission is then propagated through continued sexual contact and childbirth.

Hepatitis B is the only DNA virus that causes chronic hepatitis. (A new virus called the TT virus has identified but its clinical characteristics are as yet incompletely understood). Since HBV is a DNA virus, it can incorporate itself into the DNA of the hepatocyte. Thus, replication of the hepatocyte allows for development of HBV virus replication as well. The chronic hepatitis associated with HBV is associated with the body's immunologic attack on infected hepatocytes, not the actual infection by the Hepatitis B virus itself.

Hepatitis B has the ability to cause acute infectious hepatitis as well as a chronic form (Chronic Hepatitis B).

Hepatitis B is transmitted via percutaneous, sexual and perinatal mechanisms. Oral transmission of hepatitis B is uncommon. The incubation period is approximately 80 days. HBV rarely causes joint aches (arthralgias). Also, fever is less common. Nausea and vomiting are quite prevalent in this disease. Jaundice occurs predominantly in adults. In Children, the acute infection is usually asymptomatic. Liver function tests remain elevated for several months. In most cases, the mortality is a low, < 1 percent. It does cause chronic hepatitis as well as carrier states and has a relapse variant.

Chronic hepatitis B may relapse with episodes characterized by jaundice and constitutional symptoms (nausea vomiting at center). This situation is termed reactivation. Reactivation can occur in patients who been treated with immunosuppressants for other diseases. Severe recurrent hepatitis may occur with this event.

Acquisition of hepatitis B as an infant or during early life usually results in an asymptomatic acute infection. Subsequently, these patients go on to develop chronic hepatitis B. Chronic Hepatitis B may then develop a "healthy carrier" state. This healthy carrier state is somewhat deceptive since it is thought that this may actually be associated with the development of hepatocellular carcinoma (liver cancer).

Acquisition of hepatitis B as an adult results in an acute infection that is resolved. Adult acquisition of acute Hepatitis B usually resolves in 95 percent of cases. These patients then go on to develop immunity to hepatitis B. Five percent of adult cases develop chronic hepatitis B.

Complications of chronic HBV include:

	Cirrhosis
	Renal failure
	Ascites
	Hepatocellular Carcinoma
	Esophageal Variceal Hemorrhage

Because of these potential complications, therapy for chronic HBV has been sought. Treatment of Chronic Hepatitis B includes interferon and lamuvidine. Treatment of hepatitis B with alpha interferon has been associated with a 30 to 35 percent conversion from chronic hepatitis B to immunity. Optimal patients are those who have moderately high serum aminotransferases levels (AST and ALT) with low circulating titers of the hepatitis B virus. HBV can be measured in the blood stream with a PCR (polymerase chain reaction test) so that actual amount of virus circulating in the blood stream can be determined (in many cases, this type of test is not required.) Some patients with chronic HBV may benefit from pretreatment with steroids.

During treatment with interferon, a spike in aminotransferases levels may occur at approximately 8 weeks. This flare in serum ALT levels indicates the clearance of the infected Hepatitis B hepatocytes. This is a positive event in patients being treated with interferon.

Positive predictors of response to alpha-interferon for chronic hepatitis B are:

	Adult acquisition of hepatitis B
	ALT > 100 IU/ liter
	Hepatitis B DNA titers (via PCR) < 100 pg/ml
	Female sex
	Active hepatic inflammation assessed by liver biopsy.

Negative predictors of response to alpha interferon include:

	Early acquisition of Hepatitis B
	ALT < 100 IU/ l
	Serum Hepatitis B DNA concentrations > 200 pg/ml
	Positive HIV status.
	Coexistent Hepatitis D infection
	Minimal histologic inflammation on liver biopsy.

A vaccination for hepatitis B is now available. This should be administered to:

	Health-care workers who are potentially exposed to infectious body fluids
	Patients with chronic renal failure on hemodialysis
	Male homosexuals or promiscuous heterosexuals
	All workers and clients of institutions for the developmentally disabled
	Adolescents: Due to the high rate of sexual transmission associated with hepatitis B, vaccination has been recommended by pediatricians and hepatologists alike.

Approximately 10 percent patients treated with the current vaccine will fail to develop immunity.

Vaccination of adolescents will help to break the cycle of sexual transmission associated with HBV. By reducing the transmission rate in this group of patient, infection of the fetus from unplanned childbirth will be reduced.

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