hepatitis B

hepatitis B
Name	Hepatitis B
Synonyms	Serum hepatitis
Caption	An electron micrograph showing hepatitis B virus particles.
Field	Infectious disease, gastroenterology, hepatology
Symptoms	Often none; can include jaundice, fatigue, dark urine, abdominal pain
Complications	Cirrhosis, hepatocellular carcinoma
Onset	1–6 months after exposure
Duration	Acute or chronic
Causes	Hepatitis B virus (HBV) infection
Risks	Unprotected sex, intravenous drug use, healthcare worker exposure, birth to infected mother
Diagnosis	Blood tests for viral antigens and antibodies
Prevention	Hepatitis B vaccine, post-exposure prophylaxis
Treatment	Supportive (acute); antiviral drugs (chronic)
Medication	Tenofovir, entecavir, interferon alfa-2b
Prognosis	Acute: >90% recovery in adults; Chronic: risk of liver failure
Frequency	~296 million chronic cases globally (WHO estimate)
Deaths	~820,000 annually (primarily from cirrhosis and liver cancer)

hepatitis B is a potentially life-threatening liver infection caused by the hepatitis B virus. It is a major global health problem and the most serious type of viral hepatitis, capable of causing both acute and chronic disease. The virus is most commonly transmitted from mother to child during birth, through contact with blood or other body fluids, or via contaminated needles. Chronic infection can lead to high morbidity and mortality from complications like cirrhosis and hepatocellular carcinoma.

Signs and symptoms

Many people, especially young children, experience no symptoms during the initial acute infection. When present, symptoms can include jaundice, dark urine, extreme fatigue, nausea, vomiting, and abdominal pain. Severe acute cases can progress to fulminant hepatic failure, a rare but critical condition. The development of chronic infection often occurs silently over decades, with symptoms only appearing once significant liver damage has occurred, such as the onset of cirrhosis or signs of portal hypertension. Extrahepatic manifestations can include polyarteritis nodosa and glomerulonephritis.

Causes

The disease is caused by infection with the hepatitis B virus, a member of the Hepadnaviridae family. Transmission occurs via percutaneous or mucosal exposure to infectious blood or body fluids. Major routes include vertical transmission from an infected mother to her newborn during childbirth, unprotected sexual intercourse with an infected person, and parenteral exposure such as sharing contaminated needles among people who inject drugs. Other risks include accidental needle stick injuries among healthcare workers and exposure through inadequately sterilized medical or dental equipment in regions with high prevalence.

Diagnosis

Diagnosis is primarily made through serological blood tests that detect specific viral antigens and antibodies. The presence of hepatitis B surface antigen indicates an active infection, while antibody to hepatitis B core antigen can distinguish between acute and chronic phases. Detection of hepatitis B e antigen suggests high levels of viral replication and infectivity. Additional tests include measurement of HBV DNA levels via polymerase chain reaction to assess viral load, and liver function tests to evaluate hepatic injury. A liver biopsy or non-invasive tests like FibroScan may be used to stage liver fibrosis in chronic cases.

Prevention

The cornerstone of prevention is administration of the hepatitis B vaccine, which is highly effective and part of routine childhood immunization programs globally, as recommended by the World Health Organization and the Centers for Disease Control and Prevention. Other key measures include screening of blood donations, practicing safe sex, and ensuring infection control practices in healthcare settings. For infants born to infected mothers, immediate administration of the vaccine along with hepatitis B immune globulin as post-exposure prophylaxis is critical to prevent vertical transmission. Public health strategies also focus on harm reduction for people who inject drugs.

Treatment

There is no specific treatment for acute hepatitis B; care is supportive and focuses on maintaining comfort and adequate nutritional balance. For chronic hepatitis B, treatment aims to suppress viral replication and prevent progression to cirrhosis and hepatocellular carcinoma. First-line antiviral drugs include nucleoside analogues like tenofovir and entecavir, which are administered orally. The injectable immunomodulator peginterferon alfa-2a may be used in select patients. Regular monitoring for drug resistance and liver cancer screening with ultrasound and alpha-fetoprotein testing is essential. In cases of advanced liver failure, liver transplantation may be the only curative option.

Epidemiology

According to the World Health Organization, an estimated 296 million people were living with chronic infection globally in 2019, with approximately 1.5 million new infections each year. The highest prevalence is in the World Health Organization Western Pacific Region and the World Health Organization African Region, particularly in countries like China and Nigeria. The infection is less common in regions like North America and Western Europe. Hepatitis B contributes significantly to global mortality, causing an estimated 820,000 deaths annually, primarily from complications like cirrhosis and hepatocellular carcinoma. Widespread vaccination, notably in Taiwan and The Gambia, has dramatically reduced the incidence of new chronic infections and related liver cancer rates.

Category:Infectious diseases Category:Hepatitis Category:Viral diseases