What is Hepatitis Delta?
Hepatitis delta, also known as hepatitis D or HDV, is a liver infection caused by the hepatitis delta virus that results in the most severe form of viral hepatitis known to humans. Only those already infected with hepatitis B can acquire hepatitis delta, as it is dependent on the hepatitis B virus to reproduce.
Worldwide, more than 296 million people live with hepatitis B and of this number, an estimated 15-20 million are also infected with hepatitis delta. Coinfections lead to more serious liver disease than hepatitis B infection alone. They are associated with faster progression to liver fibrosis, increased risk of liver cancer, and early decompensated cirrhosis and liver failure.
Types of Infection
Hepatitis delta can be acquired either through coinfection (infection with hepatitis B and delta at the same time) or superinfection (infection with hepatitis D after a person has already acquired hepatitis B). A coinfection generally resolves spontaneously after about 6 months, but it can sometimes result in life-threatening or fatal liver failure.
A superinfection is the most common form of hepatitis delta and leads to a more severe liver disease than a chronic hepatitis B infection alone. Up to 90% of superinfected individuals will develop chronic infections of both hepatitis B and delta, of which approximately 70% will progress to cirrhosis (liver scarring), compared to 15-30% of those infected only with the hepatitis B virus.
There is no vaccine for hepatitis delta, but it can be prevented by getting the hepatitis B vaccine to help eliminate the risk of infection with the hepatitis B virus. Testing for hepatitis delta is a simple blood test. It is important that people living with chronic hepatitis B get tested for hepatitis delta, as they are most at risk. Getting tested may help save lives by making sure infected persons receive appropriate medical care and treatment.
About the Virus
The hepatitis delta virus is a single-stranded, circular RNA virus and is the smallest virus known to infect humans. It is unusual in that it needs specific help from the hepatitis B virus in order to infect and replicate in liver cells. The virus's defective structure requires the envelope proteins of the hepatitis B virus for its own assembly; thus, new hepatitis delta virus particles can only be produced in a liver cell that is already infected with the hepatitis B virus.