Hepatitis is an inflammation of the liver. It can be caused by an infectious agent (virus, bacteria, parasite) or a toxic product (including alcohol and certain types of medication!).

Viral forms of hepatitis are caused by viruses whose only point in common is having the human hepatocyte as their target. They manage to penetrate it through receptors which have nothing in common with each other; once inside the cells their actions are equally very different. Therefore, there is very little similarity between hepatitis A, B, C or any other. Initially, hepatitis classification was clinical rather than molecular, which explains the common term for these diseases with a very different mechanism.

Viral hepatitis is categorised from A to G, but only the first three are really significant on a clinical level. Hepatitis A and B can be prevented through vaccination.

Hepatitis A, the most harmless, is transmitted through water and food. Hepatitis B, the most virulent, is transmitted through blood or sexual relations; approximately 5 % of people infected are chronic sufferers and become carriers of the virus without experiencing any further symptoms. Hepatitis C is spread through direct contact with contaminated blood; the virus responsible is highly resistant and, as a result, up to 80 % of infections become chronic. There are vaccines against hepatitis A and B, but not yet against C.