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Hepatitis B

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Overview

The hepatitis B virus (HBV) is a double-stranded DNA virus spread through exposure to infected blood or bodily fluids, and through vertical transmission from mother to child. It may lead to a self-limiting disease requiring no treatment but can result in chronic hepatitis B, which can predispose to liver cirrhosis and hepatocellular carcinoma. 

The incubation period of HBV is around 6-20 weeks.

Epidemiology

  • The annual incidence of HBV in the UK is 0.68 per 100,000 population
  • HBV is more common in resource-limited countries

Risk Factors

  • Visiting or being born in high-risk countries
  • Close contact with people infected with HBV
  • Injecting intravenous drugs
  • High-risk sexual behaviours (e.g. unprotected sex with multiple partners)
  • Family history
  • Infants born to mothers with HBV

Presentation

Many patients are asymptomatic until liver cirrhosis, failure, or hepatocellular carcinoma develops. Features seen may include:

Differential Diagnoses

Acute hepatitis A

  • Although there is no significant difference in presentation, hepatitis A is transmitted via the faecal-oral route. An example risk factor can be eating and drinking in unhygienic places

Acute hepatitis E

  • Although there is no significant difference in presentation, hepatitis E is transmitted via the faecal-oral route. An example risk factor can be eating and drinking in unhygienic places
  • Hepatitis E classically affects pregnant people

Investigations

  • Liver function tests:
    • In acute hepatitis B:
      • Bilirubin – increased (usually >85 µmol/L)
      • ALT, AST – increased (usually 500 – 10,000 IU/L) and ALT > AST
      • ALP – may be raised to up to 2 times the upper limit of normal
      • In chronic hepatitis B, AST and/or ALT may be slightly elevated or normal
    • Hepatitis B serology – see Hepatitis Serology Testing:
      • Hepatitis B surface antigen (HBsAg):
        • Suggests the patient is infectious
        • Chronic hepatitis B is likely if this is elevated for >6 months
      • Hepatitis B e antigen (HBeAg):
        • Associated with viral replication and a higher infectivity
      • Antibody to HBe (anti-HBe):
        • Indicates an immune response and control of viral replication
      • Antibody to HBcAg (anti-HBc):
        • Indicates current or previous HBV infection and persists for life
      • IgM antibody to hepatitis core antigen (anti-HBc IgM):
        • Indicates recent (within the last 6 months) HBV infection
        • This is released first by the immune system and is gradually replaced by IgG
      • IgG antibody to hepatitis core antigen (anti-HBc IgG):
        • Indicates past infection
      • Antibody to HBsAg (anti-HBs):
        • Indicates recovery and immunity to HBV
        • If there is no anti-HBc, the person has been vaccinated (as the core antigen is not given in the vaccine).
        • If there is anti-HBc, the person has fought off a previous infection
  • HBV DNA (HBV viral load):
    • High levels indicate higher infectivity and a higher likelihood of complications developing

Management

  • 1st-line: referral to gastroenterology/hepatology and notify Public Health England
  • Pegylated interferon is used for the treatment of HBV, although other antivirals such as entecavir may also be used.

Monitoring and Patient Advice

Monitoring

Patients are followed up by liver specialists and the frequency of follow-up depends on factors such as serology results. At each follow-up:

  • Serology is monitored
  • The patient is screened for hepatocellular carcinoma
  • Treatment effectiveness and necessity are assessed

Patient Advice

  • Patients should avoid drinking alcohol as this can increase the risk of cirrhosis and hepatocellular carcinoma
  • Patients should take steps to minimise transmission to other people:
    • Avoid sharing items that may be contaminated with blood (e.g. toothbrushes and razors)
    • Avoid unprotected sexual intercourse including oro-anal or oro-genital sex until they have become non-infectious or their partner has been immunised
    • Avoid sharing needles
    • Avoid donating blood, semen, or organs

Pregnancy

Patient advice

  • The infant should be immunised against hepatitis B from birth as there is a 90% risk of contracting hepatitis B without immunisation.
  • If the infant has been immunised, breastfeeding is safe 

Complications

  • Chronic hepatitis B:
    • 4% in healthy adults, but higher if comorbidities are present such as HIV or immunosuppression
  • Hepatocellular carcinoma 
  • Fulminant liver failure:
    • In 0.1% of patients, acute hepatitis B can lead to massive immune-mediated destruction of hepatocytes leading to fulminant liver failure
  • Extrahepatic complications:

Prognosis

  • Without antiviral treatment, the 5-year cumulative incidence of cirrhosis is up to 20%
  • 5-year survival rates can be as low as 15% in patients with untreated decompensated liver cirrhosis

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