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Hepatitis D (Delta)
GMJ News knowledge hub · last reviewed August 2026 · Georgian Medical Journal
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Hepatitis D — caused by hepatitis D virus (HDV), a defective virus that can only infect individuals already infected with hepatitis B — affects an estimated 15-20 million people globally and represents the most severe form of chronic viral hepatitis, dramatically accelerating progression to cirrhosis and hepatocellular carcinoma in coinfected patients (WHO). The treatment landscape was transformed by the approval of bulevirtide (Hepcludex) — the first specifically approved HDV drug (EMA 2020; FDA 2023) — a novel entry inhibitor that blocks HDV/HBV entry into hepatocytes. Critically, HBV vaccination prevents HDV entirely — making hepatitis D one of the most completely vaccine-preventable conditions.
Key messages
Most severe viral hepatitis — bulevirtide transforms treatment
Hepatitis D is the most severe form of chronic viral hepatitis — dramatically accelerating cirrhosis and HCC in HBV-coinfected patients. Bulevirtide (Hepcludex, EMA 2020; FDA 2023) is the first approved HDV-specific treatment.
Requires HBV — entirely prevented by HBV vaccine
HDV can only infect individuals with hepatitis B — it requires HBsAg to assemble new virions. HBV vaccination therefore completely prevents HDV infection — making hepatitis D uniquely preventable through an existing vaccine.
15-20 million chronically infected
Approximately 15-20 million people are chronically infected with HDV globally — predominantly in Central and Western Africa, Mongolia, Central Asia, the Middle East and Romania. True prevalence is likely underestimated due to lack of routine testing.
Superinfection is most severe
Two forms: HDV/HBV coinfection (simultaneous — typically self-limiting, resembles severe acute hepatitis B); HDV superinfection (HDV acquired by a chronic HBV carrier — causes severe acute disease and high progression to chronicity and cirrhosis).
Bulevirtide mechanism — entry inhibition
Bulevirtide (Hepcludex) is a first-in-class entry inhibitor — a lipopeptide that blocks the NTCP (sodium taurocholate cotransporting polypeptide) receptor, preventing both HBV and HDV entry into hepatocytes.
Testing remains critical gap
Most HBsAg-positive patients are never tested for HDV antibodies — a major missed opportunity. WHO recommends testing all HBsAg-positive individuals for HDV infection.
Key statistics
HDV prevalence among HBsAg-positive individuals by region — WHO estimates
Source: WHO. Highest HDV prevalence in Central/West Africa, Mongolia and parts of Central Asia.
Glossary of key terms
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Hepatitis B and CHCCLiver diseaseHBV vaccine (HDV prevention)HIV/HDV coinfectionBlood safety
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