You can only contract this is you are also currently suffering from hepatitis B.
You can get two types of infection:
Normal co-existant infection – 90% of cases – this actually reduces the severity of the hep B infection! This is because infection with hepatitis D can reduce the replication rate of the hepatitis B virus. These people will usually make a full recovery from an unremarkable acute hepatitis.
Superinfection – 10% of cases – this greatly worsens prognosis. It is due to chronic infection with both viruses. It is not really known what causes this. It can be detected by very high levels of anti-HDV in the blood.
With both types of co-infection there is an increased risk of fulminant liver disease.
Common mode of transmission is IV drug use (in the UK). In other parts of the world it is transmitted by close personal contact.
It is common in some parts of the Mediterranean, as well as Africa and South America.
There is only one identified antigen – HDV. The test for infection with hep D is anti-HDV.
To prevent hep D, basically, you need to prevent hep B infection!