Hepatitis C is a liver infection that can lead to serious liver damage. It’s caused by the hepatitis C virus. About 2.4 million people in the U.S. have the disease. But it causes few symptoms, so most of them don't know. The virus spreads through an infected person’s blood or body fluids. There are many forms of the hepatitis C virus, or HCV. The most common in the U.S. is type 1. None is more serious than any other, but they respond differently to treatment.