Hepatitis B is a viral infection of the liver that can cause both acute and chronic disease Hepatitis B is a viral infection that attacks the liver and can cause both acute and chronic disease. The causative agent is the hepatitis B virus (HBV), a DNA virus that replicates through an RNA intermediate. Infection is a major global health problem, and its long-term consequences are largely driven by chronic infection.
Classification and general context
Hepatitis is a broad term for liver inflammation. The condition can be self-limiting or can progress to fibrosis (scarring), cirrhosis or liver cancer. Among the hepatitis viruses, the five main types (A, B, C, D and E) differ in transmission routes. Types B and C lead to chronic disease in hundreds of millions of people and, together, are the most common cause of liver cirrhosis and cancer. Hepatitis A and E are mainly spread through contaminated food or water, whereas hepatitis B is transmitted through contact with body fluids.
Transmission
HBV is found in blood and other body fluids. The virus is most commonly transmitted from mother to child during birth and delivery, in early childhood, as well as through contact with blood or other body fluids during sex with an infected partner, unsafe injections or exposures to sharp instruments. Transmission routes vary by region: in areas where infection is common, perinatal and early childhood (horizontal) transmission predominate, while in lower-prevalence settings, sexual transmission and injection-related exposure play a larger role.
Pathogenesis and clinical course
Disease severity depends strongly on age at infection. Children under 6 years of age who become infected do not usually show symptoms of acute hepatitis but are most likely to develop chronic infection. Between 80–90% of infants infected during the first 5 years of life develop chronic infection. By contrast, HBV infection in adults more often results in acute hepatitis, with a small subset of people developing acute liver failure, which can lead to death.
In acute infection, the immune response, including antibody and T-cell activity, typically clears the virus. Chronic infection, by contrast, can persist silently. Chronic infection may not show symptoms for a long time, sometimes for decades. Persistent inflammation of the liver over years can lead to fibrosis, with between 20 and 30% of adults who are chronically infected will develop cirrhosis and/or liver cancer. Liver cancer in this context is usually hepatocellular carcinoma, and the cirrhosis stage marks a major step toward decompensation.
Epidemiology and burden
Estimates of the global burden differ by reference year and methodology. The WHO fact sheet reports that WHO estimates that 240 million people were living with chronic hepatitis B infection in 2024, with 0.9 million new infections each year. An earlier WHO global report, cited by the European Centre for Disease Prevention and Control, gave a figure of 254 million people living with HBV infection for 2022, with an incidence of about 1.5 million new cases per year. For 2022, 1.1 million hepatitis B-associated deaths are estimated to have occurred globally, accounting for 83% of all viral hepatitis deaths.
Prevalence is uneven across regions. The burden of infection is highest in the WHO Western Pacific Region and the WHO African Region, where 102 million and 64 million people, respectively, are chronically infected. In children under five, the WHO estimated global prevalence of chronic infection at 0.6%, with the African Region at 1.4%, which remains far above the 2030 target.
Diagnosis
Diagnosis relies on serological and molecular tests. The presence of the hepatitis B surface antigen (HBsAg) indicates infection. Acute infection can be identified through detection of IgM antibody to the core antigen, or through HBsAg or HBV DNA in a person whose earlier HBV markers were negative. Chronic disease is assessed by diagnostic measurements such as HBV DNA level and alanine aminotransferase (ALT), along with assessment of liver fibrosis. Guidelines use different ALT thresholds; for example, the AASLD guidance recommends using an upper range of normal ALT of 25 IU/L in women and 35 IU/L in men; the WHO ALT thresholds are 19 IU/L for women and 39 IU/L for men. Fibrosis may be evaluated by liver biopsy or by noninvasive methods; determined traditionally by biopsy but now more often by noninvasive measures such as AST-platelet ratio index (APRI) or vibration-controlled transient elastography (VCTE).
Underdiagnosis is substantial. According to one summary of US data, only 25% of infected individuals are diagnosed.
Prevention
Vaccination is the principal preventive measure. The hepatitis B vaccine is 90% effective in preventing perinatal transmission if the first dose is given within the first 24 h of life, followed by a minimum of two subsequent doses. The vaccine is part of routine immunization in most countries. Globally, of the 194 WHO member states, 116 countries recommend universal hepatitis B birth dose vaccination to all newborns, in alignment with global recommendations.
Vaccine policy has become contested in some settings. In December 2025, the US public health advisory committee voted to recommend a birth dose only for infants born to mothers who test positive or whose status is unknown. The CDC adopted individual-based decision-making for parents of infants born to women who test negative, and the American Academy of Pediatrics continues to recommend a birth dose within 24 hours. The committee's vote is described by its supporters as a response to parental concerns and differences with European schedules, and by critics as likely to reduce vaccination. No new safety or efficacy concerns were cited in the review, according to the reporting No fresh safety concerns or effectiveness issues prompted ACIP to reconsider the hepatitis B vaccine birth dose.
Global elimination goals are set for 2030. By 2030, a 90% reduction in the number of new chronic hepatitis B infections and a 65% reduction in the number of deaths is to be achieved, according to WHO targets as summarized by ECDC.
Treatment
Treatment depends on whether infection is acute or chronic. Acute infection often resolves without specific therapy. But chronic hepatitis B is an incurable illness. Antiviral drugs aim to suppress viral replication, reduce liver damage and lower the risk of complications. Antiviral therapies leading to maintained HBV suppression in chronic hepatitis B and sustained viral response in hepatitis C are recommended, since they have been shown to prevent progression to cirrhosis and HCC development. Even so, successful antiviral therapy reduces but does not eliminate the risk of HCC development.
The most commonly used drugs are nucleos(t)ide analogues. Tenofovir and entecavir are preferred because of their potency and minimal risk of resistance, decompensation, and serious side effects. Interferon-based therapy is an alternative in some cases, although it is not appropriate for every patient. Treatment decisions are based on HBV DNA levels, ALT, and fibrosis. For example, the European guidelines recommend therapy for patients with HBeAg-positive or HBeAg-negative chronic hepatitis B, HBV DNA level ≥2,000 IU/ml and elevated ALT (>ULN) and/or significant fibrosis. The guidelines also address equity: from a health equity perspective, antiviral treatment for individuals with chronic HBV infection living in LMICs should be based on at least one of the following tests: HBV viral load, ALT level, or liver fibrosis.
Stopping therapy is a separate question. Some patients achieve loss of HBsAg, and guidance for some groups states that treatment should be continued until HBsAg clearance is confirmed or indefinitely in those who undergo liver transplantation.
Limitations and open questions
Several issues remain under active study. Current drugs suppress rather than eradicate the virus, because HBV DNA can persist in liver cells even when serum viral levels are low. Access to diagnosis and treatment varies widely; the lower-income settings with the highest burden often have the least access to testing and drugs. Estimates of the number of infected people also depend on survey methods, which explains some of the differences between reports. Finally, the balance between treating early (before significant liver damage) and treating later is still debated, and new guidelines continue to expand eligibility for antiviral therapy.
References
- Hepatitis Bwho.int
- Hepatitis B and C Fact Sheet What is hepatitis?afro.who.int
- Hepatitis B in the WHO European Region FA C T S H E E Twho.int
- Disease information on hepatitis B - ECDCecdc.europa.eu
- Core Concepts - When to Initiate HBV Treatment - Hepatitis B Online - Hepatitis B Onlinehepatitisb.uw.edu
- Hepatitis B Facts and Figureshepb.org
- Introduction of the Hepatitis B Vaccine—Birth Dose: Methods of Improving Rates in a Milieu of Vaccine Hesitancyncbi.nlm.nih.gov
- Hepatitis B Birth Dose Briefing Documentcdc.gov
- CDC Adopts Individual-Based Decision-Making for Hepatitis B Immunization for Infants Born to Women Who Test Negative for Hepatitis B Viruscdc.gov
- CDC panel recommends delaying birth dose of hepatitis B vaccinestatnews.com
- Hepatitis B: Symptoms, Causes & Transmissionmy.clevelandclinic.org
- Hepatitis B Guidelines: Guidelines Summary, 2016 and 2018 AASLD Guidelines, 2017 and 2018 EASL Recommendationsemedicine.medscape.com
- Update on Prevention, Diagnosis, and Treatment and of Chronic Hepatitis B: AASLD 2018 Hepatitis B Guidance - PMCpmc.ncbi.nlm.nih.gov
- EASL Clinical Practice Guidelines on the management of hepatitis B virus infection - Journal of Hepatologyjournal-of-hepatology.eu
- CDC's ACIP changes recommendations for hepatitis B vaccination for infants : Shots - Health News : NPRnpr.org
- AAP: CDC decision on universal birth dose of hepatitis B vaccine will have ‘heartbreaking’ consequencespublications.aap.org