hepatitis D virus
Meaning of hepatitis D virus: A virus too incomplete to infect anyone by itself, dependent on hepatitis B to supply the coat it cannot build.
Definition of hepatitis D virus
Hepatitis D virus is a small virus that can only reproduce inside a liver cell already infected with hepatitis B virus. It cannot make its own outer coat, so it wraps itself in the surface protein of hepatitis B in order to leave the cell and reach another. Infection with both viruses causes more severe liver inflammation than hepatitis B alone.
Why does it need hepatitis B?
Most viruses carry the genetic instructions for every part of themselves. This one does not. It can copy its own genetic material inside a liver cell perfectly well, but it has no gene for a coat, and without a coat a virus particle cannot survive outside a cell or enter the next one. Hepatitis B virus makes far more surface protein than it needs for its own particles, and the delta virus takes the surplus. Where hepatitis B is absent, hepatitis D can go no further than the cell it is already in.
What are the two patterns of infection?
| Coinfection | Superinfection | |
|---|---|---|
| Timing | Both viruses acquired together | D acquired on top of long-standing B |
| Illness | Often severe but usually short | Sudden worsening of established disease |
| Becoming long-term | Uncommon | Usual |
How does it spread and how is it found?
Both viruses travel the same routes: contact with infected blood, shared injecting equipment, and sexual contact. Transmission from mother to infant occurs but is less prominent than it is for hepatitis B alone. Because the picture looks like hepatitis from any cause, the virus is only identified when it is looked for, and testing is directed at people already known to carry hepatitis B, particularly those whose liver tests deteriorate without explanation.
Can it be prevented?
Indirectly, and effectively. Vaccination against hepatitis B prevents hepatitis D as well, because the delta virus cannot establish itself without the surface protein hepatitis B provides. No separate vaccine exists or is needed. For someone who already carries hepatitis B, however, that protection has passed, and avoiding blood contact is the remaining route.
Also known as
Used in a sentence
Serology was extended to hepatitis D virus after liver enzymes rose in a known hepatitis B carrier.
Good to know
Hepatitis D cannot be acquired without hepatitis B, so hepatitis B vaccination prevents both, and testing is directed at people already known to carry hepatitis B.
Word origin
Where “hepatitis D virus” comes from
Hepatitis joins the Greek hepar, meaning liver, to the suffix -itis, denoting inflammation.