About viral hepatitis
The term viral hepatitis is used to refer to several infections affecting the liver that, while being clinically similar, differ etiologically (different viruses responsible for the infection), epidemiologically (different distribution and frequency of infection and disease) and in terms of immunopathogenesis. In Italy, hepatitis is included among the class II diseases subject to compulsory notification (i.e. high-frequency diseases that may require control actions).
Five types of viral hepatitis are currently known to be caused by the main hepatitis viruses:
- Hepatitis A
- Hepatitis B
- Hepatitis C
- Hepatitis D (Delta)
- Hepatitis E
In about 10%-20% of cases, however, the agent responsible for hepatitis remains unknown. Other viruses potentially involved in these infections were first isolated in the 1990s, including: F virus; G virus, which is known to infect humans but does not usually appear to be clearly associated with disease; TT virus, which is frequently isolated from patients with various types of liver disease and also from healthy individuals; and SEN virus, isolated from people with viral hepatitis.
There are also viruses that can cause hepatitis of varying severity secondary to another disease. These secondary hepatitis viruses include: cytomegalovirus, Epstein-Barr virus, Coxsackie virus and herpes virus.