Hepatitis D

Hepatitis D is an inflammatory liver disease caused by the hepatitis D virus, a defective agent that requires concurrent hepatitis B virus infection to replicate and assemble new virions ^[1][3]. It occurs only in persons with HBV infection and has been classified by IARC as carcinogenic to humans (group 1) ^[1].

Acute co-infection with HDV and HBV is followed by clearance of both viruses in about 95% of cases, whereas superinfection of an HBV-infected person leads to chronic HDV-HBV infection in over 90% of instances ^[3]. Chronic hepatitis D produces more rapidly progressive liver disease than HBV alone, with 30% to 70% of chronic patients having cirrhosis at diagnosis and more than half dying of liver disease within a decade, though some studies indicate a variable and often indolent course ^[3].

Among people with chronic HBV infection, roughly 5% are co-infected with HDV, accounting for about one in five cases of liver disease and liver cancer in this group ^[1]. A meta-analysis of 282 studies estimated anti-HDV prevalence at 4.5% among HBsAg-positive individuals and 16.4% among those in hepatology clinics, corresponding to about 12 million infected persons worldwide ^[2]. Geographic hotspots include Mongolia, the Republic of Moldova, and countries in western and middle Africa, with elevated prevalence in injecting drug users, haemodialysis recipients, men who have sex with men, and commercial sex workers ^[1][2].

HDV is blood borne and follows the same routes as HBV, spreading through contact with infected blood or body fluids, sexual intercourse, and rarely from mother to child around birth ^[1]. It can also disseminate within families in endemic regions, and chronic HBV carriers are susceptible to HDV infection ^[1]. Persons lacking immunity to HBV are at risk of acquiring HBV and thereby HDV ^[1].

Hepatitis D virus (HDV) infection cannot occur in the absence of hepatitis B virus (HBV), so vaccination against hepatitis B is the cornerstone of HDV prevention, as it provides immunity against the HBV component that HDV requires for replication ^[1]. Because HDV is blood borne and transmitted through contact with infected blood or other bodily fluids, including through sexual intercourse and, rarely, vertical transmission from mother to child before or around birth, people who are not immune to HBV—either through prior natural infection or immunization with the hepatitis B vaccine—remain at risk of acquiring HBV and consequently HDV ^[1]. Chronic HBV carriers are also at risk of superinfection with HDV, underscoring the importance of HBV vaccination for susceptible individuals and the need for targeted prevention measures for higher-risk populations such as indigenous peoples and people who inject drugs, who are more likely to be affected by HBV–HDV co-infection ^[1].

1. 1 World Health Organization. Hepatitis D [Internet]. cited 23 Oct 2026. Available from: https://www.who.int/news-room/fact-sheets/detail/hepatitis-d
2. 2 Stockdale AJ et al. The global prevalence of hepatitis D virus infection: Systematic review and meta-analysis. J Hepatol. 2020 Sep. PMID: 32335166. doi: 10.1016/j.jhep.2020.04.008. PubMed: https://pubmed.ncbi.nlm.nih.gov/32335166/
3. 3 Negro F et al. Hepatitis D: A Review. JAMA. 2023 Dec 26. PMID: 37943548. doi: 10.1001/jama.2023.23242. PubMed: https://pubmed.ncbi.nlm.nih.gov/37943548/