Hepatitis B is a contagious liver disease that results from an infection by the hepatitis B virus (HBV). It can range in severity from being a mild ailment lasting a few weeks to a serious, even life threatening, lifelong illness. With proper treatment, it can be managed. Also, for many people, getting the hepatitis B vaccination can prevent them from getting HBV. You should get tested to know for sure if you have hepatitis B.