Hepatitis B is a contagious, acute disease of the liver that may become chronic. The CDC estimates that nearly 43,000 people contracted hepatitis B in the United States in 2007, although the number of reported cases is much lower because some people do not show symptoms. There are an estimated 800,000 to 1.4 million chronic cases in the United States. Globally, there are about 360 million chronically infected people, and as many as 626,000 people die of hepatitis B every year.