Hepatitis D: Description, Causes and Risk Factors:
Alternative Name: Delta hepatitis.
Hepatitis D virus is an “incomplete virus” because it can only replicate in the presence of Hepatitis B virus. Hepatitis D virus has a small single-stranded RNA genome that only encodes one virus-specific protein (“delta antigen”). This genome is encapsulated within a protein coat of HBsAg that allows the hepatitis D virus to gain cell entry. During the period when hepatitis D virus is replicating in cells, hepatitis B replication is temporarily suspended.
HDV is the only virus in the genus, delta virus. HDV is not classified into a viral family because it is a unique virus dependent on HBV. HDV is a co-infection of HBV. The envelope of HDV particles contains the Hepatitis B surface antigen (HBsAg). The production and transmission of HDV is entirely dependent on HBV to provide HBsAg. Thus, HDV is considered a satellite virus of HBV. Unlike a classical satellite virus, however, HDV does not share sequence similarity with HBV, and it can replicate independently of HBV.
There are at least three HDV genotypes: I, II, and III. HDV isolates of Genotype I have been reported in every part of the world, and the pathogenesis of Genotype I infections varies from fulminant hepatitis to asymptomatic chronic liver disease. The milder HDV II genotype is found primarily in Asia, including Japan, Taiwan, and Russia. Some sequences from Taiwan and the Okinawa islands have been assigned to a subtype of Genotype II, called Genotype IIB. HDV genotype III has been isolated only in northern South America (Peru, Venezuela, and Columbia) and is associated with severe acute hepatitis. Furthermore, HDV genotype I is the only genotype found in some locations, including Europe and North America. Multiple genotypes have been detected in Africa and in Asia. Mixed infections of genotypes I and II or II and IIb have been reported in Taiwan. Furthermore, 15 of 22 recently characterized African sequences formed new lineages and the other 7 are scattered within genotype I. Therefore, recent work has indicated that the current classification of HDV into only three genotypes is incomplete.
Hepatitis D infections occur globally, but the prevalence varies widely among countries. An estimated 10 million people worldwide have dual infections with hepatitis D and hepatitis B viruses. Hepatitis D infection occurs epidemically or endemically in populations at risk of hepatitis B virus infection, such as populations in countries where hepatitis B is endemic (e.g., Russia, Romania, southern Italy, Africa and South America); in hemophiliacs, intravenous drug addicts and others who come in frequent contact with blood; in institutions for the developmentally disabled; and, to a lesser extent, in male homosexuals. In the United States, seroprevalence may be over 50% in high risk groups such as urban injection drug users.
There are many ways to contract HDV (hepatitis D virus). Some include:
Using intravenous (IV) drugs/contaminated needles.
- Contaminated blood.
- Nail clippers.
- Sexual intercourse with an infected person.
HDV is passed most often through sharing IV drug needles with a person already infected with the virus. People that are receiving clotting factor concentrates may also be at a higher risk than most. The only way for a person to become infected with HDV is to first have type B hepatitis. If a person does not have HBV, the virus is not able to multiply itself.
Hepatitis D virus transmission can occur simultaneously with a new hepatitis B infection (“co-infection”) or can occur as a superinfection of a person with chronic hepatitis B. Transmission is similar to that of hepatitis B virus - by exposure to infected blood and serous body fluids, contaminated needles, syringes and plasma derivatives such as antihemophilic factor, and through sexual transmission. All people still susceptible to hepatitis B virus infection or who have chronic hepatitis B infection can be infected with hepatitis D virus.
Hepatitis D may be self-limiting or it may progress to chronic hepatitis. Children may have a particularly severe clinical course with common progression to chronic active hepatitis. With superinfection, symptoms due to hepatitis D infection can be misdiagnosed as an exacerbation of chronic hepatitis B infection.
Symptoms may include:
- Abdominal pain.
- Body aches and pains.
- Dark urine.
Type D hepatitis should be considered in individuals who are HBsAg positive or who have evidence of recent HBV infection. The diagnosis for Hepatitis D infection is made following serologic tests for the virus. Total anti-HDV antibodies are detected by radioimmunoassay (RIA) or enzyme immunoassay (EIA) kits. To monitor ongoing HDV infection, reverse transcriptase-polymerase chain reaction (RT-PCR) should be used. RT-PCR can detect 10 to 100 copies of the HDV genome in infected blood serum. Each of the markers of HDV infection, including IgM and IgG antibodies, disappears within months after recovery. In chronic Hepatitis D infection, on the other hand, HDV RNA, HDAg (hepatitis D antigen), IgM anti-HD antibodies, and IgG anti-HD antibodies persist.
The acute form of the hepatitis D virus is more likely to disappear on its own in co-infection cases, when a person gets infected with hepatitis B and hepatitis D at the same time. Fewer than 5% of people co-infected will develop chronic hepatitis D.
In superinfection cases, in which a person with chronic hepatitis B then gets hepatitis D, up to 80 percent of people will develop chronic hepatitis D. These cases may result in severe chronic hepatitis D that often progress to cirrhosis (end-stage liver disease) or cancer of the liver.
While no drugs are approved to treat chronic hepatitis D, liver transplantation has been shown to be an effective treatment for people with severe liver disease caused by hepatitis D. If someone is diagnosed with acute hepatitis D, symptoms are usually gone within a couple of months. There is also a form of treatment called supportive care that deals mainly with the symptoms alone.
The drug interferon may be helpful in treating disease conditions in some patients.
NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.