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Hepatitis B

Introduction

Hepatitis B virus – showing the important constituent parts

Hepatitis B is an infection of the liver, caused by the hepatitis B virus (HBV). It is the most common cause of hepatitis worldwide, and there are believed to be over 350 million chronic cases. It is endemic in Asia and the Far East (up to 10% have chronic hepatitis B), but rare in the developed world. In the UK, about 1 in 350 people have hepatitis B.

Spread occurs via infected blood – e.g. via sexual intercourse, vertical transmission from mother to baby, and historically it was also seen in blood transfusions.

The incubation period is between 6-23 weeks.

The serologically important factors, which help in determining immunisation status as well as disease status include:

All patients with hepatitis B need assessment and management.

Hepatitis B is preventable by vaccination. In both the UK and Australia, this is now part of the routine vaccination schedule in children. Usually, three doses are required to confer immunity.

Most cases in the UK are the result of injecting drug use or sexual exposure.

About 10% of cases of infection will go on to develop chronic hepatitis B. Chronic disease is defined as detectable levels of surface antigen (HBsAg) 6 months after infection.

Epidemiology and Aetiology

Presentation

May be asymptomatic, or have minor flu-like symptoms. Symptomatic individuals may present with:

Acute Hepatitis B

Maternal transmission is different

Chronic Hepatitis B

10% of cases of infection will go on to develop chronic hepatitis B. The risk of developing chronic disease depends on the age at which the infection is acquired. The risk in neonates from maternal transmission >90%, whilst in adults, it is around 10%, and in children who acquire the infection after birth the risk is even lower. Many patients are “healthy carriers” without any ongoing symptoms.

Diagnosis

Understanding Hepatitis B testing

There are several antigens and antibodies that are present during, and following Hepatitis B infection. Understanding which of these is present and when can help you identify if a person has a current or past infection, and their immunity status.

At the most simple level:

Clinical Status Positive Serological Markers
Immunity following previous natural exposure Anti-HBc (may be negative if infection was a long time ago)
Anti-HBs
Previously Vaccinated Anti-HBs
Acute Infection HBs-Ag
Anti-HBc
HBV-DNA
HBe-Ag (may be negative depending on timing)
Chronic Infection HBs-Ag – HBsAg present 6 months after exposure is diagnostic for chronic infection
Anti-HBc
HBV-DNA
(all above still positive 6 months after diagnosis)

Pathology

In chronic disease, viral DNA may become incorporated into host DNA. HbsAg is present on the surface of infected hepatocytes, and this causes T cells to induce apoptosis in these cells. The pathogenesis is different to that of HAV (Hepatitis A Virus) , where the apoptosis is not induced by the immune system, but by the infected cell itself – thus HAV does not have the ability to cause chronic disease.

Complications

Management

If acutely unwell – will need hospital admission. Otherwise can be managed in primary care, with non-urgent referral to gastroenterologist or infectious diseases specialist upon confirmation of diagnosis (positive HBsAg).

Symptomatic management is often all that is required in the acute phase. Itching due to jaundice may be difficult to manage.

It is important to check for other commonly associated infections, including HepC and HIV.

If not already done, ensure diagnosis is confirmed with serological testing, and FBC and Lots are performed.

Reducing transmission

Vertical transmission

To babies of infected mothers:

Intimate contacts

Prognosis

References

Read more about our sources

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