Hepatitis B is a disease of the liver. It's caused by the hepatitis B virus. Your liver is the largest organ inside your body. It sits under your right ribcage. The liver has many important roles. It filters harmful chemicals from your blood. It helps you fight infections and it helps you digest your food. It stores nutrients, vitamins and energy. If your liver gets infected by the virus, it becomes inflamed. Inflammation is the body's response to an injury or infection. The inflammation from the hepatitis B virus can affect your liver's ability to do its job. You can have an acute or short-term hepatitis B infection. You may have mild to severe symptoms that last a few months, or you can have an ongoing (chronic) infection.