Hepatitis B Virus (HBV): Comprehensive A-to-Z Overview
Epidemiology & Global Burden
Chronic HBV infection affects over 250 million individuals globally, representing approximately 3.5% of the world's population, and remains a leading cause of cirrhosis and hepatocellular carcinoma (HCC) with significant mortality 1, 2. The incidence is decreasing due to widespread vaccination programs and antiviral therapy to reduce viral loads in chronically infected individuals 2.
Transmission Routes
HBV transmits through:
- Mother-to-child transmission (most common globally)
- Infected blood and body fluids
- Sexual contact with infected partners
- Sharing injection equipment, razors, or toothbrushes
- Contaminated glucose testing equipment 3, 4
The virus remains viable outside the body for at least 7 days, making environmental transmission possible 5.
Diagnostic Approach
Initial Screening
All adults ≥18 years should receive hepatitis B screening at least once in their lifetime using three laboratory tests: HBsAg, anti-HBs, and anti-HBc 6.
Expanded Risk-Based Testing Populations
- Pregnant women
- Persons with sexually transmitted infections or multiple sex partners
- Current or former incarcerated individuals
- Persons with hepatitis C virus infection history
- Anyone requesting testing, regardless of disclosed risk 6
Diagnostic Markers for Disease Classification
HBsAg positivity for ≥6 months defines chronic HBV infection 3. The disease exists in distinct phases:
Immune-Tolerant Phase
- HBeAg positive
- HBV DNA >1 million IU/mL
- Normal or minimally elevated ALT/AST
- No significant fibrosis or inflammation 3
Immune-Active Phase (HBeAg-positive)
- HBV DNA >20,000 IU/mL
- Intermittently or persistently elevated ALT/AST
- Moderate to severe necroinflammation with or without fibrosis 3
Immune-Active Phase (HBeAg-negative)
- HBV DNA >2,000 IU/mL
- Elevated ALT/AST
- Anti-HBe positive
- Chronic hepatitis with inflammation 3
Inactive Phase
- HBeAg negative, anti-HBe positive
- HBV DNA <2,000 IU/mL
- Persistently normal ALT/AST 3
Treatment Indications & Goals
The 2025 EASL guidelines emphasize early diagnosis, risk stratification based on viral and host factors, and tailored antiviral therapy to prevent progression to cirrhosis and HCC 1.
First-Line Antiviral Therapies
Potent nucleos(t)ide analogues with high resistance barriers—specifically tenofovir (disoproxil fumarate or alafenamide) and entecavir—represent the treatment of choice for chronic hepatitis B 1, 7.
Efficacy Data for HBeAg-Positive Disease (after 2-3 years):
- Tenofovir disoproxil fumarate: 73% HBV DNA suppression (<60 IU/mL), 21% HBeAg seroconversion, 68% ALT normalization
- Tenofovir alafenamide: 73% HBV DNA suppression (<29 IU/mL), 18% HBeAg seroconversion
- Entecavir: 76% HBV DNA suppression (<60 IU/mL), 21-22% HBeAg seroconversion, 68-81% ALT normalization 3
Efficacy Data for HBeAg-Negative Disease:
- Tenofovir disoproxil fumarate: 93% HBV DNA suppression, 76% ALT normalization
- Tenofovir alafenamide: 90% HBV DNA suppression, 81% ALT normalization
- Entecavir: 90-91% HBV DNA suppression, 78-88% ALT normalization 3
Pegylated Interferon-α
Pegylated interferon-α-2a can be considered in patients with mild to moderate chronic hepatitis B for a finite 48-week course 3, 7. However, it achieves lower rates of viral suppression compared to nucleos(t)ide analogues:
- HBeAg-positive: 30-42% HBV DNA suppression, 29-36% HBeAg seroconversion
- HBeAg-negative: 43% HBV DNA suppression 3
The advantage of interferon therapy is the potential for HBsAg loss (functional cure) in 2-11% of patients, which is associated with higher remission rates and lower cirrhosis/HCC rates 3, 2.
Treatment Duration & Monitoring
Nucleos(t)ide analogues require long-term maintenance therapy to maintain viral suppression 2. The 2025 EASL and AASLD guidelines address withdrawal of antiviral therapy in select patients, though specific criteria require careful consideration 8.
All patients with chronic HBV should be regularly monitored during treatment for:
- Viral load suppression
- ALT/AST normalization
- Treatment adherence
- Drug resistance (though rare with first-line agents)
- Disease progression markers 4
HCC Surveillance
All patients with chronic HBV infection are at increased risk for HCC and require surveillance 1, 7. The 2025 EASL guidelines provide comprehensive recommendations for HCC surveillance, including:
- Patients with cirrhosis (highest risk)
- HBsAg-positive persons coinfected with HCV, HDV, or HIV
- Continued surveillance considerations after HBsAg loss 1, 8
Prevention Strategies
Vaccination
Effective vaccines to prevent hepatitis B are available and represent the cornerstone of prevention 1, 6.
Household and sexual contacts of HBsAg-positive persons should be vaccinated 3.
Prevention of Maternal-to-Infant Transmission
Pregnant women must be screened for HBV, and appropriate interventions implemented to prevent vertical transmission 6, 8. The 2025 AASLD/IDSA guidelines specifically address maternal-to-infant transmission prevention 8.
Behavioral Precautions for HBsAg-Positive Individuals
Persons who are HBsAg-positive should:
- Use barrier protection during sexual intercourse if partner is unvaccinated or not naturally immune
- Not share toothbrushes, razors, injection equipment, or glucose testing equipment
- Cover open cuts and scratches
- Clean blood spills with bleach solution
- Not donate blood, organs, or sperm 3
Important caveat: HBsAg-positive children and adults can participate in all activities including contact sports, should not be excluded from daycare or school, and can share food, utensils, and kiss others 3.
Special Populations
The 2025 EASL guidelines dedicate specific sections to management of special populations, HBV reactivation prophylaxis in immunosuppressed patients, and post-transplant care 1.
Emerging Treatment Goals
Current research focuses on achieving HBsAg seroclearance (functional cure), which is associated with:
- Higher remission rates after treatment cessation
- No viral rebound
- Lower rates of cirrhosis and HCC 2
The 2025 EASL guidelines discuss emerging biomarkers and evolving definitions of functional and partial cure, representing the future direction of HBV management 1.
Simplified Algorithms for Resource-Limited Settings
Recognizing challenges in resource-limited regions (particularly Africa and Asia), the 2025 EASL guidelines emphasize simplified algorithms for HBV management while maintaining efficacy 1. The 2022 Chinese guidelines set aggressive treatment thresholds at detectable HBV DNA >10-20 IU/mL, representing one of the most uncompromising approaches to prevent HCC complications 9.
Global Elimination Targets
The guidelines support global HBV elimination targets through emphasis on vaccination, screening, early diagnosis, and tailored antiviral therapy 1. The WHO published updated HBV guidelines in March 2024 to support these elimination efforts 9.