hepatitis delta virus
Meaning of hepatitis delta virus: First noticed as a puzzling new marker in liver cells of people with hepatitis B, later shown to be a separate virus.
Definition of hepatitis delta virus
Hepatitis delta virus is the alternative name for hepatitis D virus, a defective virus that cannot complete its life cycle unless hepatitis B virus is present in the same liver cell. Its genetic material is a small circular loop of RNA, unlike that of any other virus known to infect people. Together with hepatitis B it produces the most aggressive form of viral hepatitis.
Why does it have two names?
It was first recognized as an unexplained antigen found in the liver cells of some people carrying hepatitis B, and was labeled with the Greek letter delta before anyone knew what it was. It was assumed at first to be a further protein made by hepatitis B itself. Later work showed it to be a distinct infectious agent, and it was assigned the letter D in the alphabetical sequence used for hepatitis viruses. Both names remain in use, and the older one survives in the phrase delta agent.
What is unusual about it?
| Feature | Detail |
|---|---|
| Genetic material | A small circular strand of RNA |
| Outer coat | Borrowed from hepatitis B virus |
| Proteins it makes | Two forms of one antigen, and nothing else |
| Independence | None; it cannot spread alone |
The circular genome resembles the viroids that infect plants more closely than it resembles any human virus, which is why its origin is still debated. Carrying so few genes of its own, it relies on machinery belonging to the host cell for almost everything.
What does it do to the liver?
The liver damage comes largely from the immune response the infection provokes rather than from the virus destroying cells directly. Inflammation is more intense and more sustained than with hepatitis B alone. Scarring accumulates faster, so cirrhosis tends to appear earlier and at a younger age, and the risk of liver cancer developing on that scarred background is raised. Not everyone follows this course, and the pace varies with the strain and with the level of hepatitis B activity alongside it.
Where is it found?
Its distribution follows hepatitis B but unevenly, with concentrations in parts of central and northern Asia, the Amazon basin, parts of Africa, and around the Mediterranean. It is looked for far less often than it is present, so the number of recognized cases understates the total.
Also known as
Used in a sentence
Testing for hepatitis delta virus was added to the chronic hepatitis B assessment.
Good to know
The virus makes only one antigen of its own and carries no gene for a coat, so it depends completely on hepatitis B and cannot be transmitted without it.
Word origin
Where “hepatitis delta virus” comes from
Delta is the fourth letter of the Greek alphabet, matching the letter D later assigned to the same virus.