Hepatitis is an inflammatory disease of the liver, most commonly caused by a viral infection. Hepatitis caused by a virus can cause swelling of liver cells and is one of the most widespread and dangerous infectious diseases in the world. There are five major hepatitis viruses called types A, B, C, D and E. In particular, hepatitis B and C can cause chronic disease in hundreds of millions of people, and together they are the most common cause of cirrhosis and liver cancer.