Hepatitis D
Definition
According to The American Heritage Dictionaries, Hepatitis D is "an acute or chronic infection of the liver caused by an RNA virus, occurring either simultaneously with hepatitis B (coinfection) or as a superinfection in a hepatitis B carrier, usually being more severe than other forms of hepatitis". Just like hepatitis B virus, hepatitis D virus can cause both acute and chronic forms of the disease.
The delta virus cannot cause an infection by its one, probably because it is just a small and incomplete viral particle. In order to develop, in hepatitis D virus needs to be covered and protected by the hepatitis B virus. It is considered to be a chronic infection with hepatitis D virus when the virus remains in the blood for more than six months after getting infected.
In coinfection (that is when both HBV and HDV appear at the same time) most patients are able to fully recover, because that causes an acute form of hepatitis. The acute hepatitis usually has two forms of appearing: in single episode (simultaneous HBV/HDV replication) or in two episodes (sequential HBV/HDV replication). Only 2-5% of the infected persons will develop a chronic form of the hepatitis. Unfortunately, this is not the case in the superinfection (HDV infection appears after HBV infection already affected a body). In this case, between 50-70% of the infected patients develop fulminant hepatitis, in which the HDV tends to reproduce more, being in the presence of favorable medium - with a large number of hepatitis B viruses. They are more likely to become chronic carriers of the virus, almost all superinfection cases being followed by chronic hepatitis.
Short history
The hepatitis D virus(also called the delta virus) was discovered in 1978 by the Italian gastroenterologist Mario Rizzetto and molecular virologist John Gerin from Georgetown University. Italian physicians discovered that some patients with hepatitis B had another type of infectious agent in their liver cells. Later the new virus—HDV—was confirmed by experimentally infecting chimpanzees. When both viruses are present, acute infection tends to be more severe. Furthermore, patients with both infections are likelier than those with HBV alone to develop chronic liver disease, and, when it occurs, it is more severe. This rare virus depends on hepatitis B to survive and to replicate, and their combination cause important damages to the liver.
Incubation period and infectivity
The hepatitis D virus has an incubation period virus which range between 3-7 weeks. In coinfection, the incubation period is of 3 to 7 weeks, but that changes in suprainfection because of the fact that in those cases the hepatitis D virus replies faster in the presence of a favorable environment (which is constitute from hepatitis B virus). In this second case, the incubation period is only 3 weeks.