Hepatitis B

Hepatitis B is an infectious disease caused by the Hepatitis B virus (HBV) affecting the liver. It can cause both acute and chronic infections.

Symptoms may include jaundice, fatigue, dark urine, and abdominal pain, but many people, especially children, may remain asymptomatic. Chronic HBV infection can lead to severe complications such as cirrhosis and liver cancer.

Transmission occurs through contact with infectious body fluids, and the virus is notably more infectious than HIV.

Signs and Symptoms

The onset of symptoms can take up to six months after infection. Acute infection symptoms include general malaise, loss of appetite, nausea, vomiting, body aches, mild fever, dark urine, and jaundice.

Chronic infection may be asymptomatic but can lead to chronic hepatitis, cirrhosis, and hepatocellular carcinoma. Extrahepatic manifestations include serum-sickness-like syndrome, polyarteritis nodosa, membranous glomerulonephritis, and Gianotti–Crosti syndrome.

Diagnosis

HBV infection is diagnosed through blood tests that detect viral antigens or antibodies. The hepatitis B surface antigen (HBsAg) is used to screen for infection, while antibodies to the core antigen (anti-HBc) indicate past or ongoing infection.

In chronic cases, the presence of viral DNA is measured to assess viral load and monitor treatment response.

Virology

HBV is a member of the hepadnavirus family. The virion consists of an outer lipid envelope and an icosahedral nucleocapsid core containing the viral DNA and DNA polymerase.

The HBV genome is circular and partially double-stranded. It includes genes that encode the core protein (HBcAg), the surface antigen (HBsAg), and the X protein, which is associated with liver cancer development.

Prevention

The hepatitis B vaccine is highly effective and recommended for all infants and those at high risk of infection. The vaccine is typically given in three doses, providing long-term protection.

Other preventive measures include screening blood donations, safe sex practices, and antiviral prophylaxis to prevent mother-to-child transmission.

Treatment

Acute HBV infection usually does not require treatment and resolves spontaneously. Chronic infection, however, may need antiviral medications such as tenofovir or interferon to reduce viral replication and prevent liver damage.

Treatment duration varies but often extends beyond one year. Liver transplantation is considered for severe cases with cirrhosis or liver cancer.

Epidemiology

As of 2019, approximately 296 million people globally had chronic HBV infection, with 820,000 deaths resulting from HBV complications. The highest prevalence is in Africa and the Western Pacific region, with significant numbers of infections also occurring in moderate prevalence areas like China and India.

History

HBV has been infecting humans for millennia, with evidence from ancient human remains. The virus was discovered in 1966 by Baruch Blumberg, who identified the Australia antigen, later known as HBsAg.

The first vaccines were developed in the early 1980s, significantly reducing the incidence of HBV worldwide.

World Hepatitis Day is observed on July 28 to raise awareness about hepatitis B and other viral hepatitides.

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Self-assessment MCQs (single best answer)

Which of the following is the most common complication of chronic Hepatitis B infection?

What is the primary method of Hepatitis B virus transmission in high prevalence areas?

Which of the following markers is first detectable during an acute Hepatitis B infection?

Which of the following is used to confirm a past Hepatitis B infection and immunity in the absence of active disease?

Which antiviral medication is recommended by the WHO as a first-line agent for the treatment of chronic Hepatitis B?

Which of the following is NOT a route of transmission for Hepatitis B?

What percentage of adults infected with Hepatitis B clear the infection spontaneously?

Which phase of chronic Hepatitis B infection is characterised by high levels of viral replication and is highly infectious?

Which of the following vaccines is recommended for infants to prevent Hepatitis B infection?

What is the recommended treatment for acute Hepatitis B infection?