Hepatitis D – known as "hepatitis delta" - is a liver infection caused by the hepatitis D virus that results in the most severe form of viral hepatitis known to humans. Only those already infected with hepatitis B, however, can acquire hepatitis D, as it is dependent on the hepatitis B virus to reproduce.
Worldwide, more than 240 million people live with hepatitis B and of this number, an estimated 15-20 million are also infected with the hepatitis delta virus (HDV). Hepatitis D infections lead to more serious liver disease than hepatitis B infection alone. It is associated with faster progression to liver fibrosis, increased risk of liver cancer, and early decompensated cirrhosis and liver failure.
Types of Infection
Hepatitis D can be acquired either through co-infection (infection with HDV and hepatitis B at the same time) or super-infection (infection with HDV after a person has already acquired hepatitis B). A co-infection generally resolves spontaneously after about 6 months, but it can sometimes result in a life-threatening or fatal liver failure.
A super-infection is the most common form of hepatitis D and leads to a more severe liver disease than a chronic hepatitis B infection alone. Up to 90% of super-infected individuals will develop chronic hepatitis D, 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 HDV, but it can be prevented by getting the hepatitis B vaccine to help eliminate the risk of infection with the hepatitis B virus. There is a simple and easily accessible blood test for HDV. It is important that patients with chronic HBV get tested for HDV. Having the HDV test may help save lives by making sure infected persons receive appropriate medical care and treatment. It is important for patients with chronic hepatitis B infection to get tested for HDV.
The hepatitis D virus (HDV) is a single-stranded, circular RNA virus that 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 HDV’s defective structure requires the envelope proteins of the hepatitis B virus for its own assembly; thus, new hepatitis D virus particles can only be produced in a liver cell that is infected with both viruses.
Facts and Figures
Globally HDV is estimated to affect 15-20 million people. HDV co-infection is more common in parts of the world such as China, Russia, Middle East, Mongolia, Romania, Georgia, Turkey, Pakistan, Africa, and the Amazonian river basin. Globally HDV is estimated to affect 15-20 million people.
The risk of progression to cirrhosis, including the risk of liver cancer, liver transplant, and death is in the 70% range, when patients have chronic hepatitis delta co-infection along with chronic hepatitis B.
There are at least 8 different types of HDV called “genotypes,” which are associated with distinct disease progression. In general, a more severe disease occurs in genotype 1 and 3, and a milder disease in genotype 2. Although a single genotype tends to dominate in an infected person, multiple genotypes can occur in those at high risk for repeated exposure to the virus.
•Genotype 1– most common and found worldwide, especially Europe, the Middle East, North America and North Africa
•Genotype 2 – found in Japan, Taiwan and Russia
•Genotype 3 – found exclusively in Amazonian region of South America
•Genotype 4 – found in Japan and Taiwan
•Genotypes 5 - 8 – identified primarily in Africa
The hepatitis delta virus is transmitted the same way as the hepatitis B virus - through exposure to infected blood or body fluids.
High-Risk Groups for Hepatitis D:
•Intravenous drug users
•Men who have sex with men
•People with many sexual partners
•People emigrating from countries where hepatitis D is common
HDV transmission is rare among those who receive blood transfusions or hemodialysis in the U.S. because blood products are routinely screened. In developing countries, screening of blood products is not common, so transfusions and hemodialysis can be a high-risk route of transmission. Unlike hepatitis B infections, mother-to-child transmission of HDV is rare.
Because hepatitis D requires a patient to have hepatitis B, the best means of preventing HBV and HDV is the hepatitis B vaccine. The hepatitis B vaccine is the first line of defense.
For those already infected with the hepatitis B virus, you can protect yourself by not sharing needles and using protection during sex.
Many people infected with hepatitis D do not experience any symptoms. In others, it may make the symptoms of their hepatitis B infection more severe.
Testing for the hepatitis D virus (HDV) can determine whether a person has a co-infection or a chronic super-infection, as they are two different conditions with different outcomes.
Within 4 weeks after exposure to HDV, a blood test could reveal the presence of “total antibody” to the hepatitis D virus; this is known as an “anti-HDV” test. This would have to be confirmed by a positive hepatitis B blood test since an HDV infection can only occur in the presence of a hepatitis B infection.
Currently there is no approved treatment for acute or chronic HDV infection. Pegylated interferon alpha is the only drug that has been shown to be somewhat effective against HDV. It acts by stimulating the body's immune system to get rid of the virus. A small percentage (<30%) experience remission when injected weekly over 48 weeks. Oral nucleosides approved for hepatitis B have been used for HDV if interferon therapy is not possible and there is a high hepatitis B viral load. But these have not been very effective.
Currently, there is more hope for people diagnosed with Hepatitis D with promising new drugs in development.