Hepatitis delta virus

Hepatitis Delta Virus (HDV) is a unique virus that requires the presence of Hepatitis B Virus (HBV) to replicate. It is the smallest known virus to infect humans and is considered a subviral satellite because it can propagate only in the presence of the hepatitis B virus.

Overview

HDV is a defective RNA virus that was discovered in 1977 in the serum of Hepatitis B patients. It is a small circular RNA virus and is unique among animal viruses in that it requires the helper function of another virus (HBV) to replicate. HDV infection occurs either as a co-infection with HBV or as a superinfection in HBV carriers.

Structure

The HDV is composed of an approximately 1.7-kb, single-stranded, circular RNA genome. The genome is surrounded by hepatitis delta antigen (HDAg) and is enveloped by a lipid bilayer in which hepatitis B surface antigen (HBsAg) is embedded.

Transmission

HDV is transmitted through percutaneous or mucosal contact with infectious blood, similar to the transmission of HBV. It can also be transmitted through sexual contact and from mother to child during childbirth.

Clinical Features

HDV infection can present in two forms: co-infection with HBV or superinfection of a person with chronic HBV infection. Co-infection with HDV and HBV can result in a more severe acute disease with a higher risk of fulminant hepatitis than infection with HBV alone. Superinfection of a person with chronic HBV infection can result in an acute flare of chronic hepatitis B, with a rapid progression to liver cirrhosis.

Diagnosis

Diagnosis of HDV infection is made by detecting HDV RNA in serum or by detecting IgM or IgG antibodies to HDV in serum.

Treatment

There is no specific antiviral therapy for acute or chronic HDV infection. Treatment is primarily supportive.

Prevention

Prevention of HDV infection is achieved by preventing HBV infection through hepatitis B vaccination.

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