Hepatitis B

Key facts

·         Hepatitis B is a viral infection that attacks the liver and can cause both acute and chronic disease.

·         The virus is transmitted through contact with the blood or other body fluids of an infected person.

·         About 600 000 people die every year due to the consequences of hepatitis B.

·         Hepatitis B is an important occupational hazard for health workers.

·         Hepatitis B is preventable with the currently available safe and effective vaccine.

Hepatitis B is a potentially life-threatening liver infection caused by the hepatitis B virus. It is a major global health problem. It can cause chronic liver disease and chronic infection and puts people at high risk of death from cirrhosis of the liver and liver cancer.

More than 240 million people have chronic (long-term) liver infections. About 600 000 people die every year due to the acute or chronic consequences of hepatitis B.

A vaccine against hepatitis B has been available since 1982. Hepatitis B vaccine is 95% effective in preventing infection and its chronic consequences, and was the first vaccine against a major human cancer.

Geographical distribution

Hepatitis B virus can cause an acute illness with symptoms that last several weeks, including yellowing of the skin and eyes (jaundice), dark urine, extreme fatigue, nausea, vomiting and abdominal pain. Hepatitis B prevalence is highest in sub-Saharan Africa and East Asia. Most people in these regions become infected with the hepatitis B virus during childhood and between 5–10% of the adult population is chronically infected.

High rates of chronic infections are also found in the Amazon and the southern parts of eastern and central Europe. In the Middle East and the Indian subcontinent, an estimated 2–5% of the general population is chronically infected. Less than 1% of the population in western Europe and North America is chronically infected.

Transmission

In highly endemic areas, HBV is most commonly spread from mother to child at birth, or from person to person in early childhood.

Perinatal or early childhood transmission may also account for more than one third of chronic infections in areas of low endemicity, although in those settings, sexual transmission and the use of contaminated needles, especially among injecting drug users, are the major routes of infection.

The hepatitis B virus can survive outside the body for at least seven days. During this time, the virus can still cause infection if it enters the body of a person who is not protected by the vaccine.

The hepatitis B virus is not spread by contaminated food or water, and cannot be spread casually in the workplace.

The incubation period of the hepatitis B virus is 75 days on average, but can vary from 30 to 180 days. The virus may be detected 30 to 60 days after infection and persists for variable periods of time.

Symptoms

Most people do not experience any symptoms during the acute infection phase. However, some people have acute illness with symptoms that last several weeks, including yellowing of the skin and eyes (jaundice), dark urine, extreme fatigue, nausea, vomiting and abdominal pain.

In some people, the hepatitis B virus can also cause a chronic liver infection that can later develop into cirrhosis of the liver or liver cancer.

More than 90% of healthy adults who are infected with the hepatitis B virus will recover and be completely rid of the virus within six months.

Who is at risk for chronic disease?

The likelihood that infection with the hepatitis B virus becomes chronic depends upon the age at which a person becomes infected. Children less than 6 years of age who become infected with the hepatitis B virus are the most likely to develop chronic infections:

·         80–90% of infants infected during the first year of life develop chronic infections;

·         30–50%% of children infected before the age of 6 years develop chronic infections.

In adults:

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·         15–25% of adults who become chronically infected during childhood die from hepatitis B-related liver cancer or cirrhosis.

Diagnosis

It is not possible, on clinical grounds, to differentiate hepatitis B from hepatitis caused by other viral agents and, hence, laboratory confirmation of the diagnosis is essential. A number of blood tests are available to diagnose and monitor people with hepatitis B. They can be used to distinguish acute and chronic infections.

Laboratory diagnosis of hepatitis B infection centres on the detection of the hepatitis B surface antigen HBsAg. WHO recommends that all blood donations are tested for this marker to avoid transmission to recipients.

·         Acute HBV infection is characterized by the presence of HBsAg and immunoglobulin M (IgM) antibody to the core antigen, HBcAg. During the initial phase of infection, patients are also seropositive for HBeAg.

·         Chronic infection is characterized by the persistence (>6 months) of HBsAg (with or without concurrent HBeAg). Persistence of HBsAg is the principal marker of risk for developing chronic liver disease and hepatocellullar carcinoma (HCC) later in life.

·         The presence of HBeAg indicates that the blood and body fluids of the infected individual are highly contagious

Treatment

There is no specific treatment for acute hepatitis B. Care is aimed at maintaining comfort and adequate nutritional balance, including replacement of fluids that are lost from vomiting and diarrhoea.

Some people with chronic hepatitis B can be treated with drugs, including interferon and antiviral agents. Treatment can slow the progression of cirrhosis, reduce incidence of HCC and improve long term survival. Treatment, however, is not readily accessible in many resource-constrained settings.

Liver cancer is almost always fatal and often develops in people at an age when they are most productive and have family responsibilities. In developing countries, most people with liver cancer die within months of diagnosis. In high-income countries, surgery and chemotherapy can prolong life for up to a few years.

People with cirrhosis are sometimes given liver transplants, with varying success.

Prevention

The hepatitis B vaccine is the mainstay of hepatitis B prevention. WHO recommends that all infants receive the hepatitis B vaccine as soon as possible after birth, preferably within 24 hours.

The birth dose should be followed by 2 or 3 doses to complete the primary series. In most cases, 1 of the following 2 options is considered appropriate:

1.     a 3-dose schedule of hepatitis B vaccine, with the first dose (monovalent) being given at birth and the second and third (monovalent or combined vaccine) given at the same time as the first and third doses of DTP vaccine; or

2.     4 doses, where a monovalent birth dose is followed by 3 monovalent or combined vaccine doses, usually given with other routine infant vaccines.

The complete vaccine series induces protective antibody levels in more than 95% of infants, children and young adults. Protection lasts at least 20 years and is possibly lifelong.

All children and adolescents younger than 18 years old and not previously vaccinated should receive the vaccine if they live in countries where there is low or intermediate endemicity. In those settings it is possible that more people in high risk groups may acquire the infection and they should also be vaccinated. They include:

·         people who frequently require blood or blood products, dialysis patients, recipients of solid organ transplantations;

·         people interned in prisons;

·         injecting drug users;

·         household and sexual contacts of people with chronic HBV infection;

·         people with multiple sexual partners, as well as health-care workers and others who may be exposed to blood and blood products through their work; and

·         travellers who have not completed their hepatitis B vaccination series should be offered the vaccine before leaving for endemic areas.

The vaccine has an excellent record of safety and effectiveness. Since 1982, over one billion doses of hepatitis B vaccine have been used worldwide. In many countries, where 8–15% of children used to become chronically infected with the hepatitis B virus, vaccination has reduced the rate of chronic infection to less than 1% among immunized children.

As of July 2011, 179 Member States vaccinate infants against hepatitis B as part of their vaccination schedules. This is a major increase compared with 31 countries in 1992, the year that the World Health Assembly passed a resolution to recommend global vaccination against hepatitis B. Furthermore, as of July 2011, 93 Member States have introduced the hepatitis B birth dose.

In addition, implementation of blood safety strategies, including quality-assured screening of all donated blood and blood components used for transfusion can prevent transmission of HBV. Safe injection - unnecessary as well as unsafe injections - practices can protect against HBV transmission. Furthermore, safer sex practices, including minimizing the number of partners and using barrier protective measures (condoms), protect against transmission.

WHO response

WHO is working in the following areas to prevent and control viral hepatitis:

·         raising awareness, promoting partnerships and mobilizing resources;

·         formulating evidence-based policy and data for action;

·         preventing of transmission; and

·         executing screening, care and treatment.

WHO also organizes World Hepatitis Day on July 28 every year to increase awareness and understanding of viral hepatitis.