chronic hepatitis B

chronic hepatitis B
Name	Chronic hepatitis B
Caption	An electron micrograph of the Hepatitis B virus.
Field	Infectious disease, Hepatology
Complications	Cirrhosis, Hepatocellular carcinoma
Duration	Lifelong without intervention
Causes	Persistent infection with Hepatitis B virus
Risks	Perinatal transmission, unprotected sexual intercourse, intravenous drug use
Diagnosis	Blood test for HBsAg, HBeAg, HBV DNA
Prevention	Hepatitis B vaccine, post-exposure prophylaxis
Treatment	Antiviral therapy (e.g., tenofovir, entecavir)
Prognosis	Variable; depends on viral load and liver damage
Frequency	~296 million globally (WHO estimate)
Deaths	~820,000 annually (primarily from cirrhosis and liver cancer)

chronic hepatitis B is a persistent infection of the liver caused by the Hepatitis B virus. It is defined by the detection of the viral surface antigen, HBsAg, in the blood for more than six months. This condition can lead to significant liver damage over decades, including scarring and liver failure. The global burden is substantial, with major public health initiatives led by organizations like the World Health Organization and the Centers for Disease Control and Prevention focused on vaccination and treatment.

Signs and symptoms

Many individuals with chronic hepatitis B are asymptomatic for years or even decades. When symptoms do occur, they are often non-specific and can include fatigue, mild discomfort in the upper right abdomen, and joint pain. As liver disease progresses, signs of advanced damage may appear, such as jaundice, ascites, and easy bruising due to impaired coagulation. The development of complications like cirrhosis or hepatocellular carcinoma can present with more severe symptoms, including significant weight loss and hepatic encephalopathy.

Causes and transmission

The sole cause is persistent infection with the Hepatitis B virus, a member of the Hepadnaviridae family. Transmission occurs through contact with infectious blood or body fluids. Major routes include perinatal transmission from an infected mother to her newborn, a highly efficient mode common in regions like Asia and sub-Saharan Africa. Other important routes are unprotected sexual intercourse, sharing needles during intravenous drug use, and less commonly, through unsafe medical procedures or blood transfusions in settings with inadequate screening.

Diagnosis

Diagnosis is primarily made through serological blood tests that detect viral antigens and antibodies. The cornerstone is the presence of HBsAg for over six months. Additional tests assess the state of infection, including HBeAg, anti-HBe, and quantitative HBV DNA levels. Evaluation of liver disease severity often involves measuring alanine transaminase levels, performing an ultrasound of the liver, and may require a liver biopsy or non-invasive tests like FibroScan. The American Association for the Study of Liver Diseases publishes guidelines for diagnostic criteria and staging.

Prevention

Primary prevention is achieved through vaccination with the Hepatitis B vaccine, which is highly effective and part of routine infant immunization schedules recommended by the World Health Organization. For newborns of infected mothers, post-exposure prophylaxis with the vaccine and hepatitis B immune globulin is critical. Other preventive measures include screening of blood donations, practicing safe sex, and ensuring sterile equipment in healthcare settings, principles promoted by agencies like the Centers for Disease Control and Prevention and Gavi, the Vaccine Alliance.

Management and treatment

Management aims to suppress viral replication, reduce liver inflammation, and prevent progression to cirrhosis and hepatocellular carcinoma. First-line oral antiviral drugs include nucleos(t)ide analogues such as tenofovir and entecavir, which are recommended by guidelines from the European Association for the Study of the Liver. Regular monitoring of HBV DNA and liver function is essential. In cases of advanced cirrhosis, liver transplantation may be necessary. Research into new therapies, including drugs targeting the HBV cccDNA, is ongoing.

Prognosis and complications

The prognosis varies widely; some individuals remain in an inactive carrier state with minimal liver damage, while others develop progressive disease. Major long-term complications are cirrhosis and hepatocellular carcinoma, which are leading causes of mortality. The risk is influenced by factors such as high viral load, HBeAg status, co-infection with hepatitis D virus or HIV, and alcohol consumption. Surveillance with regular ultrasound and alpha-fetoprotein testing is recommended for early detection of liver cancer.

Epidemiology

According to the World Health Organization, an estimated 296 million people worldwide were living with chronic hepatitis B infection in 2019, with the highest prevalence in the World Health Organization Western Pacific Region and the World Health Organization African Region. Regions with high endemicity include China, Mongolia, and countries in West Africa. The infection causes approximately 820,000 deaths annually, primarily from liver cancer and cirrhosis. Global initiatives, such as those led by the World Health Assembly, aim for elimination through widespread vaccination and improved access to diagnosis and treatment.

Category:Hepatitis Category:Viral diseases Category:Infectious diseases