From a recent review in The Lancet:

Hepatitis delta virus (HDV) is a small, defective RNA virus that can infect only individuals who have hepatitis B virus (HBV). More than 15 million people are co-infected worldwide.

There are 8 genotypes of HDV. The hepatitis D virion is composed of a coat of HBV envelope proteins surrounding the nucleocapsid.

The nucleocapsid consists of:

- a single-stranded, circular RNA genome
- delta antigen, viral protein

HDV suppresses HBV replication but also causes severe liver disease with rapid progression to cirrhosis and hepatic decompensation (liver failure).

The range of clinical presentation is wide, varying from mild disease to fulminant liver failure.

Treatment of HDV is with pegylated interferon alfa; however, response rates are poor.

Better understanding of the molecular structure of HDV may lead to new therapeutic targets for this most severe form of chronic viral hepatitis.

References:

Hepatitis delta virus. Sarah A Hughes MBBCh, Heiner Wedemeyer MD, Dr Phillip M Harrison MD. The Lancet, Volume 378, Issue 9785, Pages 73 - 85, 2 July 2011.