The Urgent Battle Against Hepatitis D: Unlocking Global Progress and Overcoming Challenges
In the global fight against viral hepatitis, Hepatitis D (HDV) stands out as a formidable adversary. Despite being the most severe form of viral hepatitis, HDV has long been overlooked and underdiagnosed. But here's where it gets controversial: with advancements in research and a growing understanding of its unique characteristics, HDV has emerged as a critical barrier to achieving the World Health Organization's (WHO) 2030 elimination targets for viral hepatitis.
Unraveling the Global Impact of HDV
The global burden of HDV is significant, with an estimated 12 to 72 million people infected worldwide. A comprehensive meta-analysis revealed a pooled prevalence of 4.5% among hepatitis B surface antigen (HBsAg)-positive populations. Central Asia, West Africa, and parts of the Middle East bear a particularly heavy burden, with prevalence rates as high as 27% in Mongolia, 8% in Nigeria, and 6% in Pakistan. However, these numbers likely underestimate the true extent of HDV's reach due to varying diagnostic methods and incomplete surveillance.
Advancements in Understanding and Action
Over the last five years, global efforts to comprehend HDV's epidemiology have made remarkable strides. Enhanced population-based screening and more sensitive diagnostic tools have refined our understanding of HDV's prevalence and geographic distribution. Regional analyses show a wide range of HDV prevalence among HBsAg-positive populations, from 10% to 15% in Central and West Africa, 5% to 10% in Eastern Europe, and 3% to 8% in the Middle East, while most high-income regions report rates below 1%. Targeted surveys have even uncovered exceptionally high seroprevalence rates of 20% to 40% among Indigenous communities in the Amazon Basin.
These insights have prompted many countries to integrate routine anti-HDV screening into HBV management protocols and enhance surveillance systems for high-risk populations. Diagnostic and therapeutic capacities have also expanded, with standardized HDV RNA quantitative PCR assays, improved antibody testing platforms, and automated molecular diagnostic systems improving case detection and enabling programmatic screening initiatives.
Therapeutic Breakthroughs and Challenges
After decades with limited options, the regulatory approval of bulevirtide, an NTCP entry inhibitor, marked a milestone as the first targeted antiviral therapy for HDV. Bulevirtide has shown substantial reductions in HDV RNA levels and improvements in biochemical markers. Several other investigational agents, including lonafarnib, REP 2139-Mg, VIR-2218, and the monoclonal antibody libetavimab (HH-003), are now in mid- to late-stage clinical development. However, the high cost of bulevirtide and restrictive reimbursement policies limit its availability, and other emerging therapies are expected to face similar challenges, leaving patients in low- and middle-income regions with limited access to effective treatments.
Addressing Critical Barriers to HDV Control
Effective HDV control is intrinsically linked to HBV prevention strategies. Since HDV transmission requires concurrent HBV infection, robust HBV immunization programs are essential for HDV prevention. However, significant gaps remain, with adult vaccination coverage below 20% to 30% in many regions and mother-to-child transmission prevention failing in 5% to 10% of births in some low- and middle-income countries. With nearly 300 million people living with chronic HBV infection globally, sustained immunoprevention and comprehensive long-term management are crucial to reducing HDV incidence.
The Way Forward: Global and Regional Actions
To achieve HDV elimination, coordinated efforts are needed to address critical gaps in prevention, diagnosis, and treatment access. Global priority actions include expanding universal screening by implementing one-time anti-HDV testing for all HBsAg-positive individuals and improving access to affordable diagnostics. Access to emerging therapies should be enhanced through pricing mechanisms and targeted access programs in high-burden settings. HBV prevention should be strengthened by maintaining high infant immunization coverage and expanding adult catch-up vaccination programs. Linkage-to-care should be improved by raising provider awareness and integrating HDV services into existing HBV management programs.
In China, specific priority actions include integrating anti-HDV testing into national HBV screening programs, particularly for newly diagnosed HBsAg-positive individuals. Laboratory and surveillance capacity should be strengthened through expanded HDV RNA testing and the incorporation of HDV indicators into national reporting systems. Management of high-burden and mobile populations should be improved through targeted outreach programs and standardized referral pathways.
Conclusion: A Call to Action
The battle against HDV is far from over, but the progress made in recent years offers hope and a roadmap for future control efforts. By addressing the critical gaps in prevention, diagnosis, and treatment access, we can work towards a world free from the devastating impact of HDV. The time to act is now, and with coordinated global and regional efforts, we can make a significant impact on the lives of those affected by this severe form of viral hepatitis.
