Hepatitis B and C

Hepatitis B and C are major global health threats, responsible for most cases of viral hepatitis-related chronic liver disease, cirrhosis, and liver cancer. While both viruses primarily target the liver, their biology, transmission, and modern management strategies differ profoundly. Understanding these differences is critical for diagnosis, prevention, and treatment, especially given the revolutionary therapies that have transformed Hepatitis C from a chronic, debilitating infection into a curable disease.

Foundational Virology and Transmission Pathways

Hepatitis B virus (HBV) is a hepadnavirus, a DNA virus that replicates through an RNA intermediate. Its key component is the hepatitis B surface antigen (HBsAg), whose presence in the blood indicates an active infection. In contrast, Hepatitis C virus (HCV) is an RNA virus from the Flaviviridae family, notorious for its genetic diversity and multiple genotypes, which influence treatment choices.

Transmission routes are a critical distinction. HBV is highly contagious and transmitted through exposure to infected blood, semen, or other body fluids. Key pathways include perinatal transmission (from mother to child during birth), sexual contact, and sharing of needles or other drug-injection equipment. HCV is primarily transmitted through direct blood-to-blood contact. While sharing needles is a major route, historical transmission via blood transfusions (largely eliminated after 1992) and less common routes like needlestick injuries or shared personal items like razors are also possible. Sexual transmission of HCV is inefficient but occurs at higher rates among men who have sex with men, particularly those with HIV.

Clinical Vignette: A 28-year-old pregnant woman presents for prenatal care. Routine screening returns positive for HBsAg. This immediately raises concern for perinatal transmission risk to her newborn, necessitating post-exposure prophylaxis for the infant with HBV vaccine and hepatitis B immune globulin within 12 hours of birth.

Natural History: From Acute Infection to Chronic Disease

The clinical course post-infection defines the long-term burden of disease. Following exposure, both viruses can cause an acute hepatitis infection, which may be asymptomatic or present with non-specific symptoms like fatigue, nausea, abdominal pain, and jaundice.

The body's ability to clear the virus differs drastically. For HBV, the risk of developing chronic infection—defined as the persistence of HBsAg for more than six months—is inversely related to age. Approximately 90% of infected infants, 25–50% of children aged 1–5 years, and less than 5% of immunocompetent adults progress to chronic hepatitis B. For HCV, the opposite is true: about 75–85% of newly infected adults will develop a chronic infection.

It is this chronic liver disease that drives morbidity and mortality. Persistent viral replication incites ongoing inflammation and immune-mediated injury, leading over decades to fibrosis (scarring). As fibrosis progresses, it can culminate in cirrhosis, a state of advanced, irreversible liver scarring. Both HBV and HCV significantly increase the risk of developing hepatocellular carcinoma (HCC), the most common type of primary liver cancer. This risk is elevated even in the absence of cirrhosis in HBV, and primarily in the setting of cirrhosis for HCV.

Diagnostic Evaluation and Screening Imperatives

Diagnosis relies on specific serologic and virologic tests. For HBV, the cornerstone is detecting HBsAg. Additional tests like hepatitis B e-antigen (HBeAg), antibodies, and HBV DNA viral load help determine the phase of infection and guide treatment. For HCV, screening begins with an antibody test, which indicates exposure. A positive antibody test must be followed by an HCV RNA PCR test to confirm active, current viremia and measure the viral load.

The high proportion of asymptomatic chronic infection makes screening programs essential to identify infected individuals for treatment. Universal screening is recommended for HBV in pregnant women, infants born to infected mothers, and people born in regions with high HBV prevalence. For HCV, the U.S. Preventive Services Task Force recommends a one-time screening for all adults aged 18 to 79. Targeted screening for both viruses is crucial for high-risk groups, including people who inject drugs, incarcerated persons, and those with HIV.

Modern Management: Suppression vs. Cure

The management goals for HBV and HCV reflect their different virology. For chronic Hepatitis B, the goal is not eradication but durable viral suppression to prevent liver damage and reduce transmission. First-line oral antiviral agents are entecavir and tenofovir (in its disoproxil fumarate or alafenamide forms). These are potent nucleos(t)ide analogs with high barriers to resistance that effectively suppress HBV DNA replication with long-term use, often for life.

The landscape for Hepatitis C has been utterly transformed. The era of interferon-based therapy, with its severe side effects and modest cure rates, is over. Today, treatment uses direct-acting antivirals (DAAs), which are oral drugs that target specific non-structural proteins of the HCV virus (NS3/4A protease, NS5A, NS5B polymerase) to halt its replication. DAA regimens, typically given for 8 to 12 weeks, are well-tolerated and achieve sustained virologic response (SVR), defined as undetectable HCV RNA 12 weeks after completing therapy, in over 95 percent of patients. SVR is considered a cure, as it is associated with the elimination of the virus, halted progression of liver fibrosis, and a dramatically reduced risk of liver cancer and all-cause mortality.

Clinical Vignette: A 55-year-old man with a history of intravenous drug use 20 years ago is found to have positive HCV antibodies during a new patient visit. An HCV RNA test confirms chronic infection with genotype 1a. He is started on a pan-genotypic DAA regimen for 8 weeks. Follow-up testing 12 weeks post-treatment shows undetectable HCV RNA, confirming he is cured.

Prevention and Public Health Strategy

Prevention rests on vaccination and harm reduction. A safe and effective vaccine exists only for Hepatitis B. It is a three-dose series and is recommended for all infants and unvaccinated adults at risk. Hepatitis B vaccination is the primary tool to prevent infection and its long-term consequences, including HCC. There is no vaccine for Hepatitis C.

For both viruses, harm reduction is vital. This includes screening blood products, using sterile equipment for all injections, and providing comprehensive syringe services programs for people who inject drugs. For HBV, additional measures include post-exposure prophylaxis for exposed individuals and antiviral prophylaxis in certain immunosuppressed patients to prevent reactivation.

Common Pitfalls

1. Misinterpreting HCV Antibody Results: A common error is equating a positive HCV antibody test with an active infection. The antibody only indicates past exposure. Failing to follow up with an HCV RNA test can miss patients who have cleared the virus spontaneously, or worse, fail to diagnose those with active infection who need treatment. Correction: Always confirm a positive antibody test with a quantitative or qualitative HCV RNA test to determine current infectivity and need for therapy.

1. Delaying HCV Treatment Due to Perceived Barriers: Clinicians may avoid treating patients with active substance use, mental health conditions, or limited social support, assuming they will not adhere to therapy or be re-infected. Correction: DAA regimens are short, simple, and highly effective. Treatment should not be withheld based on these factors. Engaging patients in care and providing support can lead to successful cure and is a critical step in reducing community viral transmission.

1. Overlooking HBV Reactivation Risk: When initiating immunosuppressive therapy (e.g., for cancer chemotherapy, rheumatologic diseases, or organ transplantation) in a patient with past HBV exposure (positive for hepatitis B core antibody, anti-HBc), there is a significant risk of HBV reactivation, which can cause severe hepatitis. Correction: Screen all patients for HBsAg and anti-HBc prior to starting immunosuppressive therapy. Those at risk require prophylactic antiviral therapy with entecavir or tenofovir.

1. Inadequate Follow-up After Cure: Achieving SVR (cure) for HCV eliminates the virus but does not instantly reverse advanced cirrhosis. Patients with established cirrhosis prior to cure remain at elevated, though reduced, risk for hepatocellular carcinoma. Correction: Patients cured of HCV who had advanced fibrosis or cirrhosis prior to treatment must continue lifelong surveillance for HCC with twice-yearly ultrasound imaging.

Summary

• Hepatitis B and C are leading causes of chronic liver disease, cirrhosis, and hepatocellular carcinoma worldwide, but differ fundamentally in virology, transmission, and management goals.
• Chronic Hepatitis B is managed with long-term viral suppression using potent oral antivirals like tenofovir or entecavir, while Hepatitis C is now curable in over 95% of cases with short-course, well-tolerated direct-acting antiviral (DAA) regimens.
• Diagnosis requires specific testing: HBsAg for HBV, and an antibody test followed by HCV RNA confirmation for HCV. Universal and risk-based screening programs are essential to identify the asymptomatic infected population.
• Prevention hinges on vaccination for HBV (no vaccine exists for HCV) and robust harm-reduction strategies to interrupt blood-borne transmission.
• Clinical vigilance is required to avoid pitfalls such as misinterpreting HCV antibody tests, delaying treatment, and failing to prevent HBV reactivation during immunosuppression.