Global Alert and Response (GAR)

Hepatitis B


Introduction


- What ?
- How ?
- Who ?
- Where ?
- When ?
- Why ?

Hepatitis is a general term meaning inflammation of the liver and can be caused by a variety of different viruses such as hepatitis A, B, C, D and E. Since the development of jaundice is a characteristic feature of liver disease, a correct diagnosis can only be made by testing patients’ sera for the presence of specific anti-viral antigens or antibodies.15, 23, 31

Of the many viral causes of human hepatitis few are of greater global importance than hepatitis B virus (HBV).10, 15, 23, 31

Hepatitis B is a serious and common infectious disease of the liver, affecting millions of people throughout the world.6, 10, 15, 23, 31

The severe pathological consequences of persistent HBV infections include the development of chronic hepatic insufficiency, cirrhosis, and hepatocellular carcinoma (HCC). In addition, HBV carriers can transmit the disease for many years.10, 23, 30, 31

Infection occurs very often in early childhood when it is asymptomatic and often leads to the chronic carrier state.

More than 2 000 million people alive today have been infected with HBV at some time in their lives. Of these, about 350 million remain infected chronically and become carriers of the virus.6, 15, 23, 38, 51 Three quarters of the world’s population live in areas where there are high levels of infection.

Every year there are over 4 million acute clinical cases of HBV, and about 25% of carriers, 1 million people a year, die from chronic active hepatitis, cirrhosis or primary liver cancer.51

Hepatitis B has also been called type B hepatitis, serum hepatitis, homologous serum jaundice.23, 31

What causes the disease?
Hepatitis B is caused by the hepatitis B virus (HBV), an enveloped virus containing a partially double stranded, circular DNA genome, and classified within the family hepadnavirus.10, 15, 23, 30, 31

The virus interferes with the functions of the liver while replicating in hepatocytes. The immune system is then activated to produce a specific reaction to combat and possibly eradicate the infectious agent. As a consequence of pathological damage, the liver becomes inflamed.

HBV may be the cause of up to 80% of all cases of hepatocellular carcinoma worldwide, second only to tobacco among known human carcinogens.15, 38, 51

How is HBV spread?
HBV is transmitted through percutaneous or parenteral contact with infected blood, body fluids, and by sexual intercourse.10, 11, 15, 23

HBV is able to remain on any surface it comes into contact with for about a week, e.g. table-tops, razor blades, blood stains, without losing infectivity.15, 31

HBV does not cross the skin or the mucous membrane barrier. Some break in this barrier, which can be minimal and insignificant, is required for transmission.31

HBV is a large virus and does not cross the placenta, hence it cannot infect the fetus unless there have been breaks in the maternal-fetal barrier, e.g. via amniocentesis. Still, pregnant women who are infected with HBV can transmit their disease to their babies at birth. If not vaccinated at birth, many of these babies develop lifelong HBV infections, and many develop liver failure or liver cancer later in life.23

Sexual intercourse with multiple partners or with persons who have multiple partners can be dangerous. One should not judge by appearance: most infected people look perfectly healthy and have no symptoms of disease, yet may be highly infectious.

All persons who are hepatitis B surface antigen (HBsAg) positive are potentially infectious. The many millions of people around the world who become HBV carriers are a constant source of new infections for those who have never contracted the virus.31

Blood is infective many weeks before the onset of the first symptoms and throughout the acute phase of the disease. The infectivity of chronically infected individuals varies from highly infectious (HBeAg positive) to often sparingly infectious (anti-HBe positive).

Hepatitis B is the only sexually transmitted infection for which there is a protective vaccine.23

Who is susceptible to infection?
Susceptibility is general. Only people who have been vaccinated successfully or those who have developed anti-HBs antibodies after HBV infection are immune to HBV infection.

Persons with congenital or acquired immunodeficiency including HIV infection, and those with immunosuppression including those with lymphoproliferative disease, and patients treated with immunosuppressive drugs including steroids and by maintenance haemodialysis are more likely to develop persistent infection with HBV.

Following acute HBV infection, the risk of developing chronic infection varies inversely with age. Chronic HBV infection occurs among about 90% of infants infected at birth, 25-50% of children infected at 1-5 years of age and about 1-5% of persons infected as older children and adults. Chronic HBV infection is also common in persons with immunodeficiency.10, 15, 23, 31

Where is HBV a problem, globally?
The world can be divided into three areas where the prevalence of chronic HBV infection is: high (>8%), intermediate (2-8%), and low (<2%).23, 42

High endemicity areas include south-east Asia and the Pacific Basin (excluding Japan, Australia, and New Zealand), sub-Saharan Africa, the Amazon Basin, parts of the Middle East, the central Asian Republics, and some countries in eastern Europe. In these areas, about 70 to 90% of the population becomes HBV-infected before the age of 40, and 8 to 20% of people are HBV carriers.15

In countries such as China, Senegal, and Thailand, infection rates are very high in infants, and continue through early childhood. At that stage the prevalence of HBsAg in serum may exceed 25%. In Panama, New Guinea, Solomon Islands, Greenland, and in populations such as Alaskan Indians, infection rates in infants are relatively low and increase rapidly during early childhood.15

Low endemicity areas include North America, Western and Northern Europe, Australia, and parts of South America. The carrier rate here is less than 2%, and less than 20% of the population is infected with HBV.15, 23

The rest of the world falls into the intermediate range of HBV prevalence, with 2 to 8% of a given population being HBV carriers

Click here for: World distribution map

When is hepatitis B contagious?
The most important mode of HBV transmission globally is perinatal, from the mother to her newborn baby. If a pregnant woman is an HBV carrier and is also HBeAg-positive, her newborn baby has a 90% likelihood to be infected and become a carrier. Of these children, 25% will die later from chronic liver disease or liver cancer.15 

Another important mode of HBV transmission is from child to child during early life resulting from blood contact.11

All patients with acute hepatitis B are HBeAg positive, and therefore highly infectious and careless contact with their blood or body fluids can lead to HBV infection.

HBeAg-positive specimens contain high concentrations of infectious virions and HBV DNA, in contrast to anti-HBe positive samples, in which the number of hepatitis B virions is substantially reduced.

Why is there no treatment for the acute disease?
There is no specific treatment for acute viral hepatitis B.23

Hepatitis B is a viral disease, and as such, antibiotics are of no value in the treatment of the infection.

The use of adrenocorticosteroids in the management of acute, uncomplicated hepatitis B is not indicated because they have no effect on the resolution of the underlying disease process, and may increase the rate of relapse. Early treatment of acute hepatitis B with steroids may result in the development of persistent infection. Corticosteroid therapy is only to be used in patients with chronic active hepatitis who are symptomatic, HBsAg negative, and who have severe histologic lesions in liver biopsies.31

The therapeutic effectiveness of interferon on the course and prognosis of acute hepatitis B is not known.23

Haemodialysis, exchange transfusions, cross-perfusion, and immune globulin (IG) containing high titres of anti-HBs (HBIG) do not affect favourably the course of fulminant hepatitis.

Therapy for acute hepatitis B should be supportive and aimed at maintaining comfort and adequate nutritional balance.23

Specific antiviral drugs such as lamivudine, a second generation nucleoside analogue, are available, and others are under development, but these drugs have not been evaluated for the treatment of acute hepatitis B.


World distribution map

From: World Health Organization. Introduction of hepatitis B vaccine into childhood immunization services, Geneva, WHO, 2001 (unpublished document WHO/V&B/01.31; available on request from Department of Vaccines and Biologicals, World Health Organization, 1211 Geneva 27, Switzerland)51

Geographical distribution of chronic hepatitis B virus infection. (Note: The boundaries and names shown and the designations used on this map do not imply the expression of any opinion whatsoever on the part of the World Health Organization concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. Dotted lines on maps represent approximate border lines for which there may not yet be full agreement.)


Prevalence of hepatitis B in various areas

 

% of population positive for

infection

 

Area

 

 

HBsAg

 

anti-HBs

 

neonatal

 

childhood

 

 

Northern, Western, and Central Europe, North America, Australia

 

 

 

0.2-0.5

 

 

4-6

 

 

rare

 

 

infrequent

 

Eastern Europe, the Mediterranean, Russia and the Russian Federation, Southwest Asia, Central and South America

 

 

 

 

2-7

 

 

 

20-55

 

 

 

frequent

 

 

 

frequent

 

Parts of China, Southeast Asia, tropical Africa

 

 

 

8-20

 

 

70-95

 

 

very frequent

 

 

very frequent

From: Zuckerman AJ. Hepatitis Viruses. In: Baron S, eds. Medical Microbiology, 4th ed. Galveston, TX, The University of Texas Medical Branch at Galveston, 1996:849-863,52 with permission.

 

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